Tickets in California for DL have been this way for years, and I have used them many times. All DL tickets have an expiration date of some kind. I never had any problem with it. The only possible problem would be if you couldn't use it up in time, otherwise there is no drawback. However I really like the idea of buying a 7 day and spliting it between two trips, which if you can afford to do, saves more in the long run.
I think we may see more of these in the future as the black market for partially used WDW passes is getting very active.