If it peels it's an adhesion problem but even if it is sanded underneath the peel other things affect adhesion.Nooshie's right,the best time is somewhere after it's flashed off.If you let it cure sometimes the tape will tear at the paintline and rip away,making it a pain to get started again.Pull the tape about 180 degrees and if it rips once cut the edge with a blade.Be real carefull with blue fineline because it has a habit of rolling out from under the clear or paint,definately cut it loose if it's dry.