Is it possible to get off ssri medication after decades of being on them?

Possibly: If you've been stable with depressive symptoms for a year or so, discuss this with your psychiatrist. Some people need to be on antidepressants indefinitely because they've had multiple episodes or only partial recovery. For these, it can be preventative of further illness. If your doctor feels it's appropriate with your history and current status, s/he can help you create a tapering schedule.

Yes: Any person on ssri can be gradually weaned off them w/o s/e. However, the question worth considering is - why were you on this for decades anyway? Usually, this recommendation is consistent with a h/o chronic, recurrent depressive episodes, in which case lifelong rx might be indicated. Discuss with your psychiatrist.