This is definitely a question that cannot be given a definitive answer because it is yes and no. It is very dependent on the specific make and model of the kart. Some karts could be said to have a “shelf life” in that they will flex out depending on the tubing that is used. Other karts (usually on the stiffer side) seem to almost never wear out as long as you keep the components in good shape. My kart is an 08. The axle in it is a few years old, having been replaced when it was bent. The spindles were both original until last year at rock island when I wrecked in qualifying after hitting a piece of lead at the apex of the right hander. The seat is original and in the same position from 08. Rear bearing were run multiple years from original and since replaced with SKF ceramic bearings. This model arrow did not have the gusset on the rear cross member from the factory and did crack in 09. I found the crack before it broke completely. Rewelded and also put in gusset. No problem since. The left seat strut cracked 2 years ago and had to be rewelded. Around that time the steering upright cracked at the top where the shaft bolts in. The upright is removable and I replaced it. Lastly, the frame cracked at the right front a few weeks ago at the jacksonville race. The kart wasn’t handling as well as usual so I started looking and found it. Welded it up and picked up the time I needed instantly. So anyway, through all this I still feel this kart is just as good as a new arrow. 2 years ago I was curious myself and went to test it against a brand new kart that was the exact same year and model that I had sitting around. Same engine, tires, and exact same setup. Everything was exactly the same and the karts ran within a tenth of a second on a track over 1 minute long with the older kart being faster.
Back in 96 I had a top kart that was 28mm tubing that I raced in jr. The kart was very fast for about 1 year. After that it only ran well for a short time if it had new tires. The kart was so soft the RF would gradually bend up from the counter clockwise track we raced at.
I have had similar experience with margays but they last much longer. Many have run margays for 5 years or more and they are as fast as they were new. Eventually they start to break like the arrow at the rear cross member and then other places. The frames become very soft and corner weights will change significantly from session to session.
Tony Karts and the rest of the OTK karts I would have a difficult time buying used because they are so soft that if you bend a front end component the frame will also need straightened. I can’t really attest to them being flexed out because I don’t know if I’ve seen one straight long enough to get to that point. You will hear many talk about the big teams replacing the OTK karts after every race or two. On the other hand I know some that have taken good care of their karts and have won big events on Tony Karts a few years old. Granted these karts weren’t raced 20 events a year for 3 years, but they had significant time on them. I would however, be very skeptical to think that an OTK kart could handle the amount of races my arrow has and still be as fast.
In general, many of the Euro karts have a tendency to be very soft. You can’t argue the overall success of the OTK line and many manufacturers appear to be following suit in frame design and construction. Simply look at the frame layout of the OTK kart and then compare to a Top kart, Birel, Praga, etc. Paint them all the same color and you’d be hard pressed to tell them apart.
Overall frame design of many manufacturers does not vary much from year to year. I would guess if you found a 4 year old tony kart brand new in a box the only differences from a new one today would be basically cosmetic.
I apologize my post wanders and is pretty unorganized, but I hope you find it helpful.