I've been using INK for 2 years now and I have never had any problems with it not lasting. I'd definitely recommend using either Clear Flubber or Cover Flubber as your base. (Clear for normal wear and Cover for more of an overlay. I think it's stronger).
It is really important to use INK's lamp though, as Dolly Dimple says.
Are you also giving the bottles a good stir and a shake before using?
This is what I do:-
Sanitise
Very thorough Dry cuticle work and then shape the nails.
Remove shine from nail plate (not etching).
Use INK's Dehydrator thoroughly over each nail and around free edge.
Apply Flubber (1 coat for basic gel polish, extra for overlays). Cap free edge.
Apply ILac, cap free edge. (Usually 2 coats but some may need 3 - usually pastel shades)
I usually just apply Rock Top next, but some people apply a coat of Clear Flubber, then Rock Top. I haven't needed to do this and obviously it takes longer and uses more product, but useful for those more heavy handed clients!