When the number of cards in tour list is equal to your deck size, voila!
I missed this the first time I read your comment. Smart stuff! It does mean you have to count your deck, but you can avoid that most of the game coz you know you're still well in Deck 1. So later on, count the deck once or twice and realise, ok, I'm 3 cards off - now I just count 3 draws. So it would be a hybrid approach.