Really, every lock in every dungeon, whether on a door or a treasure-chest, should have an accompanying key (usually in possession of an NPC, occasionally lost but still likely located somewhere within the dungeon) and finding those keys is likely to be much easier and more reliable than attempting to pick the locks.This is a philosophy I wholeheartedly endorse and one I try to employ when designing my dungeons as well. I definitely bore it in mind while writing The Cursed Chateau, although I'll admit right now that I didn't play completely fair on that score.
I tend to view dungeons as at least partially as puzzles. To be fun, puzzles need to include all the pieces necessary to get the whole picture. That doesn't mean any puzzle has to be easy and indeed some of the most satisfying puzzles to put together are the most difficult ones. That's why I think having a key for every lock in the dungeon is essential. Without them, you're pretty much demanding that every party must included a thief and that's a bad design in my opinion. Even leaving aside the issue of whether thieves ought to be included in OD&D at all, I don't like the notion that a party must have a member of class X or class Y to succeed and that's just what having locks without keys does.
So, this is an insight I'll be bearing in mind in all my future endeavors. I think I actually have a good track record on this overall, but, like everything, there's always room for improvement in one's dungeon design.