It's a waiting game and it depends a bit on where you are geographically as to how long you wait. I know people who've been on the list for several years (east coast) and one friend who was on the list for two months (Arizona) when his call came. You do have to be ready at a moment's notice, because the call can come any time and you don't have a lot of time to get to the hospital because lungs only last so long in transit.
It is so hard struggling everyday ,