A couple of years ago I planted some white cherry tomatoes up in July with the hope of a crop for christmas. I kept them in the dining room next to the radiator and in front of the window. I got 3 toms for christmas, but a decent crop in feb. I pruned the plant right back, watered and fed it, and it started to grow again. I got some more toms around may, pruned and fed, and then it cropped right through the summer, finally dying off in October - My wife had insisted that I put it outside as she was so sick of it by then! Overall it probably put out around 100 fruit, and lasted from July 2003 to October 2004.
A tip that I was given which worked in order to force the last toms to ripeness was to put a bin bag over the top of the plant to heat thing up...
