Yea well I had a thought the other day
Lets say youv got over a 100 dvds to get though and is still growing and If something was to happen during the time and you could watch any anime and the stuff you preordered kept coming, or you was burn out and stopped for a while and/or just found an new hobby or had other things to do,
You'd be left with 100s of anime unwatched and still is coming in,
Best thing is to watch til you have at least have 3 more left and buy non preorders so at least that way you can wait for the preorders you want to come out while your watching the ones you've got