Scuffing Epoxy Primer

I am using PPG Omni epoxy primer on my project. The tech sheet states that if it isn't top coated within 48 hours (I think) it has to be scuffed before you can top coat it. I have been priming as I go and virtually none of the car will meet the top coat time frame. My question is........ once the epoxy is scuffed, is it good until you top coat it, regardless of time? Or...does the same time frame apply once it has been scuffed? I am trying to plan out my attack and need to account for this critical part of the process. Thanks for the help! L8r

Jim