What determines the length of a fig plants dormancy? Is it strictly light and temperature or are there other factors...eg water, fig type etc? Do plants that go dormant earlier, all else being equal, break dormancy earlier in the spring?

There are probably several factors, but day length and temperature are probably the biggest. Don't think breaking dormancy is affected by when dormancy began.

Soil temp might be a factor, in addition to air temps. It is for sprouting corn and cucurbit seeds.

Plants from colder climates, such as Asian pears, break dormancy later than relatives from warmer climates, as a mechanism to avoid killing buds and or new growth through exposure to late spring freeze or frost.

Some things break dormancy, but may not flower is there has been insufficient chill during dormancy.

Hi Njfred,
IMO, not a matter of time but a matter of conditions especially temps.
As soon as temps are above 20°c in the day and around 10° in the night, the figtrees will break dormancy. If there is no or not enough light you'll get leggy and yellowish growth ...

So IMO, temps are the key parameter for breaking dormancy.

I don't recall the terminology but it is said that after a plant goes into dormancy there is a minimum period over which the plants stay in natural dormancy. After this natural (length of ) period if the ambient are suitable for growth, it will wake up and break the dormancy. However, if temperatures are low (or kept low) the plants will stay in dormancy (extended dormancy) until temperature are above a certain temp (probably 45F). This is my understanding after reading about it a while ago.