With Descent 2, it is not that often I reach the end of the OL deck even once, let alone cycling the Deck over (and over).
Is that the average experience for OLs?
I miss OL Powers.
Generally, unless the players are VERY unlucky or make some very bad decisions you will be hard pressed to cycle through the deck. There are some cards that make it slightly more likely, but generally I expect to only get one use out of each card.
Then again, there are occasional rounds where I have 12-14 of my 15 cards in hand and from then on I basically have all of them at hand all the time and it gets very frustrating and annoying for the players until the game is done.
"Death on Wings" and "Fat Goblin" are the only quests that I have seen that happen so far though.