Congrats on the heated greenhouse! It really depends on how much you are willing to pay for your tomatoes for the heating bill, where you live to determine cloudcover and solar irradiance, etc. If money is of no concern, most locations around the US can grow year round in a heated greenhouse with full Solar exposure, though the quality suffers a little in December and January in many places ... they need supplemental, usually high intensity lighting.

But if you have that licked and pay for your heat, probably 90% of the country can theoretically grow. Exceptions that do not have enough light at this time are Seattle, and probably and the northern parts of the states that border Canada, depending on the cloudcover they get.

As for the plants themselves lasting, if you have a suspension system to progressively lower them and have no disease problems LOL, there is no reason you can't keep growing the vines in theory. The problem is keeping disease out in this sort of bottling up weather, because once it takes hold the plants are beat from production, it is economical to give a rest and start over when you reach diminishing returns and this will vary with the weather and change. Plus at some point you will want to clean out all those buckets, which depends how clean you keep them and light tight that the they are.

Best luck
PC

Well money is always a concern on heating as I watch propane use closely as I rarely run the heater during the day unless its rainy and cold. I am always trying to improve things to save on heating costs. This GH is positioned east-west and gets full sun, I have a single 52in exhaust fan I use when warm enough otherwise I keep it closed off. Internally I move air with 4 box fans from the ceiling. The tomatoes are on a suspension system in the center as the peak is 12ft and I have tomatoes to the top now. My biggest problem is with whiteflies attacking my peppers, I have traps out and spray daily. The tomatoes are doing well, good growth and still bearing new tomatoes.

BTW I have canned 62 qts of tomatoes since Sept of this year.