I'm thinking of monotheist Binlor play where you are in danger of exhausting the dungeon's supply of walls
You're more likely to run out of walls because Binlor's boons remove them then because you were smashing them to generate piety. Secondly, unless you need to go nuts with Stone Heart to break down a 75% resist boss there aren't even enough repeatable Binlor boons available to knock out that many walls.
I don't see a point to going "monotheism" Binlor, especially if you find him early. Unless you desperately need stone skin against the boss (in which case racking up magic resistance doesn't help you, so you won't be racking up as many boons and won't run into wall limitations), converting out just makes too much sense, and saving popcorn for a mid-battle level-up is too big a sacrifice in my view.