Hi Guys,
The secret to one strut kites endurance is to fly them within their wind range. If flying them powered in the upper half of their wind range where you depower to the point of trailing edge flutter, then its time to rig down.
One struts are best in their lower to mid range. Used in the right application, they will last fine. Not for kite looping unless on a foil in lighter winds.
Don't leave them flapping in the wind on the beach when not being ridden. Either throw a bunch of sand on them to stop them fluttering, or deflate the leading edge and roll up around the strut.
You can repair the trailing edge, have a sailmaker of kite repairer like the Sail Doctor to apply a sticky back canopy cloth over the last 3 or 4 inches and sew around the edges. It will add a tiny amount of additional weight, but shouldn't really be noticeable when flying.
Hope this helps,
DM