My sister was my guinea pig, I did the full shellac system in hot pop pink, then a layer of cnd shiney t/c, applied the velveteen and patted it down well. It stayed on for the night it was required and came off during the following day, but she was left with the shellac which has lasted for the amount of time we expect on her (normally 10 days as her job uses equipment such as slitters and is very heavy on her hands).
I'm sure it must last longer on others, but so long as mine stays put for one evening and looks great after then I know what to advise. But definitely use a good t/c and pat down well xx