I have to confess I have been a lurker for several months, gaining knowledge from all on this board and their tremendous experience. Now maybe is the time where I can get into a discussion. In regards to keeping containers outside for the summer, a system we use is called Pot-in-Pot and I have not seen it discussed here before.  We use this with the standard industry "5 gal nursery cans"  Basically you dig a whole large enough to insert a container into buried up to the lip. This is the permanant "socket" pot. It always stays in gorund and is never removed. Then you put the other container that your plant is growing in, inside this socket pot.  There are many benefits to this simple idea:
1. The roots are insulated from extremes of hot and cold just like if the fig was planted in the ground.
2. It keeps plants from blowing over in the wind
3. Root mass seems to grow better than above ground containers
4. Can't overwater as it drains into the socket pot and then from there into ground, no bath tub effect
5. Easy to hook up to drip irrigation
6. Easy to adjust plant by turning top pot
7. Just lift out to take in for winter, or put into in spring
8. Should air prune roots
9. Only dig the hole once, not every year!

If you are using the same size and brand container you will need a spacer between the 2 or they will jam together and stick.  We use a soda can on it's side. cheap and readily available.  Beer cans work too! This keeps the top container with the plant up a little and allows some air circulation.  We also changed ours and leave them about 3-4" above soil level for the socket pot. this way we put wood chips in between the containers to keep down weed growth. We originally put ours on 2' centers but if you spaced a little farther apart you could get a weed eater in and around easier.  You can use this with any size container although 1 and 2 gallon probably aren't worth the trouble.  We chose the 5 gal because it is easily available and to standardize.

I may not have written well enought to explain so here is a link that shows a picture and tells about it http://www.lsuagcenter.com/en/crops_livestock/crops/nursery_crops/Potinpot+Nursery+Production.htm

PTAggie--Looks like a great idea! Thanks for posting it, and welcome to the forum!

PTAggie do you grow FIGS using this system?  My trees are tiny yet, so this may be

Pami - Stored might be a better term than grow.  We have a small nursery on the farm. This is the system we keep plants in for sale and also keep some nursery stock over the winter.  We do 50' rows 25 pots to a row 2 rows per aisle. We will be overwintering some figs in this system but havent so far. Overwintered mainly conifers, apples, peach, berry bushes, We do our growing inground.  It just seems like an easy way to move and set plants and not worry about holes in the sides to keep roots from growing into ground etc

PTAggie
I, and I believe some others, do pot in pot summer growing but with different intention. The main advantage is that the plant roots go out through the holes and gets extra nutrients from the soil added between the two pots as well as the plant can be relatively easily removed from the outside (socket) pot in the fall.
I have some fig plants in 5-gallon pots that are placed inside 7+ gallon pots. The 5-gallon pots still have good number of side holes near the bottom and the space between the two pots is filled with garden soil mix with compost while the inside pot is with light well drained mix. The roots go out to graze for nutrients in the soil between the two pots (and they really circle well outside around the internal pot and that is OK. In the fall it is easy to lift the 5-gallon pot with the plant and prune the roots and take it to cold storage room in the basement for the winter instead of the big 7+ gallon pot.
This way the plant gets nutrient from garden soil between the two pots in addition to the fertilizer added to the 5-gallon plant pot. I believe the root pruning frequency is also minimized by annual pruning in the fall.

OttawanZ5
That makes sense for a good growing situation, still easy to remove since the roots do not go into the actual ground just another container.  It is a good system if you don't mind putting plants in the same place each year.  As for me I have dug enough holes in my life so I can be satisfied with the same spot each year