most bike purchaces i have made with the intention of keeping them "forever" (10+ years), however i have never owned a bike for more than 3 years. usually, it'll end up i buy a bike thinking i will like this or that about it, then decide it really wasnt all it was cracked up to be, and sell it.
the bike i kept for 3 years was my 1998 zx6R, it was the 2nd 98' 6r i owned, first one i had for more than 1 year, so maybe you could say i really rode that make/model for 4 years. then sold it for a TZR250 (street legal) thinking it would be lighter, cheaper and more fun. well it was 2 of those things, you guess which two..
looking back (always 20/20 aint that great?), i shoulda kept that damn 98' 6r. i'd still have it today and i would have had it for 7 years now.
Last bike i had was a 10R, bought it expecting to never sell it, credit cards fucked me and had to sell it. been saving for another once since, cant wait to buy it flat out with cash then keep it "forever" ..... this time for realz tho !!!