I have a jar of u40 sitting around. Used it on my first five or so cork handles. Then I quit messing with it, probably couldn't pick out which rods have it and which don't. 

It’s not the cork that benefits from sealing. It’s the fills.  So you just seal the entire handle and maintain the integrity and durability of the filled spots.  And the corks is easier to clean.

As someone whom bought and sold rods quite a bit...I had been a long time rod wrap user to keep my handles pristine.  Not as 'permanent' as U40 and my cork was chalky new when I took the wrap off.  However, rod wrap wasn't waterproof and would start fraying after some use.  Last year I stumbled on the greatest handle tape I've ever used.  It's called Fusion grip tape, and it is silicone, non-advesive tape that bonds to itself and forms a waterproof barrier.  It's grippy and looks sleek.

 

 

Here it is on a foam handle (abu villain)

 

 

I also use clear heat shrink tubing, but mainly because I like the two-tone black/cork combo.  Here is a Daiwa BLX with fusion tape and heat shrink.