There's no way that there's an actual answer for this. It completely depends on your situation.

Basically IMO spin them every few weeks and check true on the brakes and see if they're still free and the bearings are silent, eyeball the rims to see if they're getting very worn, and wiggle them to see if the bearings are still properly adjusted. Fix anything you find.

As for spoke tension, IMO as long as the wheel is still true they're probably fine. I do give the spokes a twang and listen. They're somewhere in the octave above middle C for me.