If I were to leave a beer for more than a few weeks I'd get it off the yeast. Most ale yeast ferment best at mid to low 60s, so as the yeast starts to slow down at those temps, I'd raise it up a few degree every other day or so once the hydrometer shows fermentation is complete (1-2 weeks usually).
Once you raise the temp it might appear as though the yeast is working again. And it might be, slightly, depending on how complete the fermentation was before you raised the temp, but it's probably more due to the fact that you are increasing the volume of wort, thereby pushing the air out of the fermenter, and bringing CO2 out of solution since warmer beer can't hold as much CO2 as colder beer. Nothing to worry about, just wanted you to know in case you saw bubbles and wondered.
If'n I was you, I would ferment at low 60s and once they hydrometer showed fermentation basically complete, I'd raise the temp for a couple of days or just pull it out and call it good. If you can keep the temp at near 70 or so for aging, that would be best.