My current kites all have 100 hours each on them. They look almost new. I have been kiting a long time. I kite a lot and I use the gear very hard but I don't subject it to unnecessary wear and tear.
My longest used kite had 300 hours on it and it was pretty ragged out. It worked fine but the fabric was porous and it took some skill to avoid stalling it.
My TT's have 4-500 hours on them. They're fine. I regularly ride on of them over the beach so the sand polishes out the scratches in the bottom. ;-)
I ride directionals now almost exclusively and they are pushing 150 hours. There's a few hazed spots on the rail and near the fins but no dings. My previous surfboard died after 160 hours. It cracked in the middle under the front foot and delaminated. I had fixed twice but that was a waste of time.
It is best economically to keep your gear and ride it to death. Replacing a quiver of kites every year is very expensive and the price of used gear is too low to improve the change over price. I have tried variations of change frequently, trade in, sell privately etc.
On the other hand, it's really nice to have new gear and it is important to monitor lines and bars and stuff to make sure they are still safe to use.
Once you are a competent rider then using the gear doesn't wear it all that much. The thing that really kills gear is dragging it around on the beach, crashing it into shore break, and leaving it on the beach flapping in the sun and wind.
It is best to use your gear as much and as hard as possible. Your aim should be to destroy your gear through use as quickly as possible. Keeping gear for too long means you are not kiting enough.
