Lifespan would depend on;
-Amount of days/time used per season (no. of kites in quiver)
-Correct inflation usage
-If kite/struts are left inflated on beach, in car, or in the sun
-Where kite is used and landed (ie sand beach, estuary, grass, gravel)
-How often the kite is dropped hard or in the surf
-If the kite kite is stored dry and clean
-Brand of kite, material, stitching and colour
Bar and lines would be the first to go if the kite have had a good life, with assisted take off and landings on clean area. Friends have sold kites a season old that have rarely been dropped and are as new. I would guess an average of 2-3 years, but I like new ones