You might want to consider using Airtime Valve traps - http://www.airtimekite.com/index.php/airtime-kite-bladders/valve-repair/valve-trap/valve-trap.html
. They sandwhich the valve shloulder with a thin but very flexible and sticky adhesive foam, making an adhesive bond on both the underside and top-side of the valve shoulder. Nice big diameter and third adhesive layer to make the bond to the bladder. I've been using them for about 6 months thus far, with excellent results.
Airtime claims they are 5 times more durable than standard stick-on valves - they must be doing some sort of accelerated testing on which this claim is based.