Yes, if your order is for more than one Merlin Annual Pass, these would all have to be collected at the same time. For example; you wanted to collect 2 Passes on Saturday and the remaining 3 Passes on Sunday, this would not be possible. All 5 Passes would need to be printed at the same time.
Merlin Annual Passholders have up to 8 weeks from the expiry date of their existing pass to take advantage of the renewal rate.
Once a renewal has been purchased, you will have 8 weeks from the date of purchase to collect any renewed Pass(es).