About a week ago I installed the full body set on my husbands iPhone 4.
I used a hair dryer on med setting for about 30-40 minutes for each side to help cure the shields.
He then waited 24 hours before first using his bumper and so far he has had no problems with the edges lifting or shifting from the bumper going on or coming off.
I think the key is to make sure that the edges of the shield do not extend beyond the edge of the glass in the least little bit and be careful not to press too hard with the squeegy because that can cause some stretching along the edges and corners. I dont think stetched edges and corners will ever lay down properly no matter how long you wait for it to cure.