Escaping from random encounters

What's your policy fleeing on random encounters?
In which cases is morally acceptable to escape a fight?
Do boss fights become too easy if you never escape random encounters, because you are too leveled up for the boss?
Does the game become more boring if you escape from fights frequently?

For me, pretty much never. I guess it depends what mechanisms the game has to avoid random encounters (repels, phantom rings, etc.) if you have a reason to.