The corneal integrity is never “fully restored” to its pre-operative state after undergoing LASIK.
This means that should a patient require an enhancement surgery years after, the corneal flap created during the first surgery can be lifted up for that purpose. It must be noted that only an eye surgeon with a special instrument is able to re-lift the flap. To be fair to LASIK, it is not common for the corneal flap to move by itself under most normal circumstances.
This re-lifting does not mean the corneal flap adherence will further weaken. The corneal flap will still heal on its own as it did during the first LASIK procedure. There are other factors one should consider carefully before proceeding with a LASIK enhancement though. The best option is to discuss with your ophthalmologist the risks vs benefits of an enhancement before you come to a decision.