Ive only had it for about 3 months and its at a south window in our basement guest room, so yes it dries out between waterings.. cause i forget about it. lol. someone gave it to me and it was pretty bad off! they had it basically sitting in water all the time... said it liked it that way. but i didn't think so- as i have read that they like well drained soil just like other gesnerads. so i immediately repotted it and it put out new growth - but i dont think its ever been dormant. do i cut off all the foliage and set it in a dark place and not water it to let it go dormant?

I've found a page that gives some good information. However, he advises uprooting the tuber in dormancy, and I suppose that's a good idea if you think there's some rot that needs to be pruned away. But once you've gotten it established and it's had consistent good care (sometimes forgetting to water can be good, LOL), you might just set the pot aside in a cool, darker spot to overwinter.
My species Sinningia are doing pretty well with me giving water when dry year round- perhaps a skootch extra when blooming. They summer outside on a south porch (covered, so little direct sun), and seem fine. Those I have slow down in winter but don't go dormant (two are in bloom right now, but one is trying to tell me it's time I cut it back and let it sleep the rest of winter). Here's the link:

Gloxinia Care and Culture
The page has some annoying adverts to go round but I think the info is sound.

I grew miniature sinningias that way, I haven't grown florist gloxinias in twenty years or more. With the minis, I kept them in constant growth unless they started dying back on their own, when as perlite said, I'd cut back on frequency of water...not totally, because for the minis, no water=death, but only watering perhaps twice a month, till I saw it pushing out new growth again.
I would imagine something similar would work fine for florist glox, but don't know.

I uproot my Sinningia speciosa (florist gloxinia) tubers when dormant just to change out the potting mix. It helps remove decaying peat moss and any fertilizer salts that flushing didn't get. Otherwise, I'm not sure there's a good reason to uproot them, and I have been known to let them go through a couple cycles before changing out their mix. Also, this plant was once part of the genus Gloxinia, which is why they are often referred to as florist gloxinia, but a revision has occurred and they are now known as Sinningia speciosa. There are many hybrids of this species, and a large number of species within the genus.

Thanks for all your help everyone! I did uproot this one... and snipped off all the leaves except for the very tip which didn't have any spots, and I'm trying to root that. We shall see how that goes. :-) It is currently in a sealed bag with AV soil mix I have. I probably won't let it sit for as long as they say... (90 days)... but who knows.

just an update... there are two little green sprouts on this! :) was happy to see that it hadnt died. :)

In the second photo, the leaf showing spots is powdery mildew which has infected into the leaf tissue. The only thing you can do is treat it as it appears or cut the leaf off. My opinion is to cut the leaf off to keep it from spreading. Once in the tissue it will always be there.

Dave