Consider that the partial formula I just shared, combined with the increase in levels, results in immensely powerful gods. Generally, a CR at or above 100. If a party can handle a creature of that kind of CR, the experience is not cheap. The PC's are just seriously big and bad, and may be in line for divine ascension themselves (a trick I have never adjudicated yet).
No experience that is hard enough to pull off can be cheapened. Knowing that it could happen is like buying a lottery ticket. You can't win if you don't play, but playing is so far from being likely to win, you might as well not play.
Between epic level magic, divine dirty laundry, things like the "last word" from Dead Gods, and similar, the death of a god might be accomplished by some very seriously prepared, determined, focused, and nigh unto maximum possible powered PC's. Then again, they are still more likely to die, as said god is likely to very quickly spot the hole(s) in their plan.
Also, killing off every last worshipper is not enough. You also have to kill off every person who fears this god, or habitually says their name. This would mean a paladin could not likely ever go after Bane in FRCS. Then again, unlikely is the key word either way.
If the PC's can't one day threaten their divine enemies, why continue to adventure past a certain point? They likely would retire. Also, if the PC's can't ever maybe even possibly defeat (notice I didn't say kill) a god, don't use Deities and Demigods-It is for the campaign where PC's at least have the chance.
Overgods-eh. Might be worth statting for intellectual purposes, but otherwise, why bother?