I tanned all year round for years.... omg from like 1998- 2000 and again from 2004- 2006.. again from 2007 - 2009 when i finally stopped. I have sun damage and sun spots... i definitely think i over did it.. but it DOES make you feel good. That's why its so addicting.
I think moderation is key... they make special home units for season depression. That might be cheaper and less ugly to you skin... and provide enough sun to give you a boost. I'd maybe check that out.