I don't claim to be an expert but my experience is:
If the patch is peeling off in an area where it isn't being battered by water then it probably hasn't been prepared properly, my boat had this from a previous owner and I am pretty sure they sanded down the tube but not the back of the patch! re-did with new patch, sanded both sides and stuck with Polymarine 2 pack glue, no further problems
If there is a leading edge anywhere near the water flow at the rear underneath of the tubes, forget it, you will not get it to stick with anything as it will eventually give in and start to peel back from the leading edge. Take it to a pro and save yourself a lot of heartache!
How long seams and tubes last depends on who makes them and is a bit of a sore point with yours truly so I won't start down that road!! But most people reckon that Avon are some of the best - how old is your boat? I have heard stories on here of Avon tubes lasting 20 years plus, mine started giving problems after 300 hours of use. Anywhere between those two extremes