Street bikes, 7 years
Counting dirt bikes/minibikes and snowmobiles, 11 years.
First bike I bought a couple days after I turned 16, a ratty 1982 Suzuki GS450"A", meaning it was the two-speed semi auto version. Learned to ride on that. Great for a road test since you couldn't stall it...just like a scooter, twist the gas and go. It ran well enough, and would hold 70-75 on the highway without too much issue....grades required WOT to keep speed but on a downhill I could get 90 out of it. Not too shabby. Problem was the guy I bought it from had apparently had a stroke or something while riding, and put it in a ditch at like 30 mph (and that's why he was selling it). The oil pan was smooshed in the front and it would randomly hemorrhage a few ounces of oil out now and then. Still I rode it to school and discovered "joyriding"....going for a ride with no particular destination in mind. Had so much fun on it. Could go blow an entire evening cruising around, and since it was only a 450, only burn like a gallon or two of gas. It returned high 40's....which considering it was only 22hp, isn't all that great I guess in comparison.
Note the duct taped seat and mismatched wheels, and the oil speckling in the dirt underneath it.
Sold that about 3 months later, for what I paid, and bought a 1985 Honda Magna V30. Really nice shape. 500cc V4....rated at 65hp, so for a 500 it was pretty fast. Felt like a rocket compared to the Zook. Ran like a swiss watch for the 2 years I owned it, only thing I ever had to do was replace the (original) plug wires as one started shorting out. Highways were effortless and even had some passing power. It would run to about 110 given enough room, and if you took it easy would give mid-50's back for economy.
But eventually the itch to upgrade came again, wanted another V4, and really the only choices were a V65, that bike's big brother, or a Vmax. I'd heard the V65's were much more problematic than the V30s, cam issues, overheating seemed to be a near universal problem in hot weather, and 2nd gear blowing out.
Ended up with my '97 Max.
Kept this the longest to date, 3 full seasons and about 22k miles. However I made the mistake of taking some demo rides at Americade, namely on a brand new Z1000, and that was the beginning of the end for my Max. I couldn't afford a new bike but the upgrade itch had returned once again. Not that the vmax wasn't fast enough....it wasn't stable enough. And it had a few other annoying traits that I'd been unable to resolve. A deal on an 03 Z1000 came along so I sprang on it.
The Max was hard to see go, but I got over it pretty quickly when I no longer had to fear for my life if I encounter a frost heave mid-corner or a tar strip at 120mph.