Its nice to hear of someone keeping a gecko for 8 years these days, you must be doing something right with him.I also know that it is not good to him, it will shorten their lifespan indeed. I kept it at a room temperature in Hong Kong, e.g. 18-33 deg. celsius. And I fed it banana, baby fruit, cricket, meal worm when he was young (6 months old, cause he refused other food I have tried). When he got older, I fed him grasshopper, pinky mice, small mice (pre-killed), super meal worm, and all kind of fruit (sweet kinds). He is now eight-year-old.
Cheer,
Charles