Our experience was that you could only book das for a park you are in.
And yes, DAS does at times give you a return time hours later. Our ratatouille DAS was at least 3 hours out, when we got it just after entering the park. It’s based on the standby time. So if the standby time is 4 hours, the DAS return time is similar. And you cannot book another DAS until you use the one you have. ILLs are not available to prebook for DAS.
Exactly what happened to us in November for any worthwhile ride wait times were literally 90 minutes or longer… so with limited park hours and needed down town and when you cant rope drop or say stay til closing depending on time… how many rides are you getting to go on when its busy? Again DAS was made to avoid standing in a que physically which is all i ask for… it does not allow me or anyone else to magically click a button or walk uo to a ride and say hey i wanna ride this now.. which may i add it should NOT do all im saying is when i am at Hershey which charges a stupid amount of money for an express pass at times i can literally walk up to a ride and get in instantly and i assure you. Their process is ridiculous when it comes to getting one you literally need to walk to GS after entering the park tell them you need one take a pic and sign a piece of paper.