This is what one of my tomato plants
looked like 2 days before Thanksgiving, when I finally picked them all & brought them in the house.
It didn't start getting chilly here (below 50 during the day) until November, but we had lots of rain so the tomatoes were splitting & needed to come off the vines. Now they're in a box on my kitchen counter, where they're turning red & getting put into the frige.
have been indoors for several weeks now, & are doing great. I still have beets left in the ground that I'm pulling up as I want to cook them, & finally have green onions coming on like crazy! I thought I planted them too late or something, as they didn't do anything until the weather cooled off!
Let us know how long you can keep that lettuce going in their little shelters!