Hey all,
I learned a trick to keeping the vanes back when I was a little kid and just started in bows. I put a drop of glue on the leading edge of the base (the flat accross section, we arent looking at the sides here). it takes the brunt of all the wear and keeps the vanes on by starting the material of the target around the vane. then it should last as long as the fletching part can.
I also learned that if you do the same thing on the very back and run a small line of glue down the side of the base, starting at the front dob and running to the rear dob. (You should have on the plastic gloves at this point) I run my finger down the side to smooth it all out.
my arrowd fletching lasted for a long long time. the bases stayed glued on with out tearing or begining to peal even when the vanes were getting all wavy. I had to cut them off and replace them becuase the "fin" portion wore out before the base even started to peel.
I hope that helps. remember its just my 2 cents.