I plan on taking a lot of cuttings this fall/ winter. As to get them to to the tree stage more quickly, is there any reason why I can't just use larger ( longer) cuttings. Most of mine have been 6-8" or so but why not 24-30"? I realize that I will get less trees, but I would take that trade off. I was thinking of starting these in large Tupperware containers with just 1/3 or so in sphagnum moss and the rest of the branch outside the moss. This would be a "winter air layer" without the parent plant. Am I on to something or asking for trouble?

While i never rooted stick that large i think it should be ok try it in mean time you can
 airlayer another large branch next season in 1 or 2 gallon container with a cut out in it with clear tape on inside and out to see the root development.

Example

I tried air layering this year and would not propigate my figs any other way. It's too easy! The problem is, the cuttings I will be collecting are not my trees. I do not have full access to them all the time. I have seen all kinds of air layering and can't understand why anyone would bother with all the crazy contraptions. 1 gal pot slit open, duct tape, a couple stakes, that's all you need. When roots poke out of the bottom, it's ready!

Your very right nothing fancy needed no hormones nothing simple water bottle cut in half and duck tape. !
Have many examples.  ; )

Skip the water bottle, right to 1 gallon. Open top, no tin foil, no plastic wrap.

LOL i like your thinking in some cases here water bottle works well when not a lot of room.
Example is these twins with water bottles that were cut short even shorter.
From 2011

I have successfully rooted "Logs", 1-2" diameter 24-30" long.  There was a thread a while back and Jon said it was the same regardless of the size of the cutting, and I found this to be true.  When the roots develop, the branches and leaves develop a lot quicker, or so it seems.

My experience with large cuttings is that they do better when the whole thing except the top 1/2" or so is buried in perlite.  See this thread. 

You can use a large trash bag with drainage holes cut in the bottom, a 55 gal drum, cardboard box lined with plastic, a large sterlite container or make your own.  As long as it has good drainage you should be fine.  When I leave the top half sticking out, the top half dies.

Aaron,

If you want to get a head start on your cuttings (and you have early access to the trees), you could try etiolating the limbs before you remove them.  I've outlined the process in other threads.  Basically, just wrap the are you think will be  your root zone with black electrical tape (sticky side out) several weeks before you take the cuttings.  It will begin the process of converting the cells.

I can't explain why, but in the past I have had worse luck with longer cuttings than shorter ones.  In theory, they should work out better since there is more material to store energy.  It has not been my experience.

Good luck.

Longer cutting don't necessarily get you there any faster. Also, you have to keep a large piece of wood from drying out.

I think you up the odds if you take those large pieces and cut them up into several smaller pieces and root them. As Jon pointed out, a larger piece comes with difficulties, such as drying out and the need for more roots fast to maintain that larger piece. Having said that, you certainly may have success, but I don't think the larger piece will necessarily translate into a faster producing tree in the end.

To say that a longer cutting will not necessarily produce fruit earlier would be to say that an air layer would not necessarily produce fruit earlier. If I took your collective advice, I figure as long as I could keep humidity in check I could make it work. Or at least give it a whirl. I have proven that thicker cuttings produce faster growing trees. 1-2" x 8-10" cuttings produced 40" of growth in 5 months (from when I put them in soil). My standard cuttings are about half of that.

Fwiw, I buried a spare chunk I pruned last fall about 1 1/2" in diameter and between 18" and 24" in my garden. I sunk the whole thing about 2-3" deep, no protection, through the winter. As I expected, nothing came up in the spring. I wrote it off. Then, in early July I saw a single shoot pop out of the ground. Now it is over 18" tall with several smaller shoots, outperforming most of my smaller cuttings. There could be several other factors at work here, but I am impressed.

I've grown trees from various sized cuttings and have not noticed any particular advantage of larger pieces. In fact, I've had mixed results with large scion, some growing fast some very slow. I think other variables are at work such as variety, how much stored energy in a particular piece, temperature, soil mix, humidity, etc. One key factor for me has always been how soon I potted up and how large the pots used. That and soil mix are key for me to getting a cutting off to a quick start.

I use a potting mix of 50/50 pro mix HP and pine bark fines. I fert w 50/50 14-14-14 and pelletized lime. I have added a little water soluble miracle grow and Superthrive, but not sure if that did anything really. I currently have 80 varieties. The 40" in 1 year is my fastest. Slowest growing has been black Jack with almost no growth at all. It was purchased as a 3 gallon at a nursery this spring and has just sat there since may. I up potted in early August hoping to encourage some new growth. I will have a crazy amount of those 40" ones to trade come fall/ winter. It is an unknown variety I call "Sorrento".

I've put a couple of small logs (maybe 4 inches around with 10+ rings and 2 feet long) completely buried in my compost pile. Within a couple weeks they have tons of roots. In other week (or less) they bud and in another week have 15+ leaves and a foot of growth. I've never even come close to mimicking that kind of explosive growth in a pencil sized cutting.

I seem to have much more rapid growth from large cuttings, too. 

Has anyone had success with rooting longer branches? It sounds to me like the two major issues are 1) getting enough of the branch to root in order to sustain the top growth. And 2) providing enough humidity to get it rooted without it drying out. I'm thinking that this would make a fine greenhouse. Has anyone tried larger grafting? Possibly a 2 year old branch?

I have had good success with larger cuttings between 18" and 24". I keep them in used topsoil bags or trash bags with damp moss or perlite just like smaller cuttings(placed in the shade). The key, like with any cuttings is keeping humidity high. Put the cuttings in 1 bag with the moss, place that bag inside another bag and use a spray bottle to water in between the two bags then tie off with a rubber band band or string. This way, the water will evaporate in the "chamber" and keep humidity high but will not rot the cuttings from constant direct contact in the first bag.
All cutting rooting times varies, usually long cuttings take longer for me. This is the same method i use with uprooted suckers with few roots. Works very well but requires patience.