Valentino Rossi admits he learnt nothing during his barren two-year spell with Ducati.
The seven-time champion moved to the Italian squad in 2011, but after claiming 79 victories across the previous 11 seasons he suffered his first win-less campaign on the Desmosedici.
While Rossi admits to frustrations at such a record, he said his biggest disappointment was being unable to help improve Ducati's competitiveness.
Nicky Hayden was Ducati's best qualifier in the 2012 season finale at Valencia, finishing 1.659s off pole - a bigger gap than the marque's deficit in Rossi's first race back in 2011.
"They say that if you get through a difficult spell you get stronger. We'll have to see. In my opinion, it hasn't taught me anything," Rossi told Italia1.
"Obviously I've been disappointed with the results. I'm disappointed with the fact that I haven't been able to sort out the bike and make it a winner, and even if not a winner not managing to improve it, to make some steps forward. This is what I missed.
"I didn't need to live two difficult years. However, maybe they'll be useful to enjoy more the upcoming years with Yamaha.
"I don't think I've lost anything. In fact, I'm in shape and charged up.
"These two years will turn out to be useful to enjoy more the upcoming ones."
In light of Casey Stoner retiring from the sport at 27 - and with Yamaha team-mate Jorge Lorenzo, 25, recently claiming he will re-evaluate his future at the end of 2014 - Rossi was asked about his own future in the sport.
He said he hoped his MotoGP ambitions would be fulfilled over the next two seasons, but that even then he would be keen to stay in motorsport.
"My idea is never to quit," he joked.
"This is what I've realised these last few years, in the sense that I'd like to always remain a racer while I can, because after bikes I'll be able to race in cars: obviously not at the level of bikes; perhaps with the same commitment but in less important series.
"Never say never, who knows. But I hope [his two-year Yamaha spell] is the final one because it would mean it's gone well.
"I think one should do his own sport as long as he is competitive and feels like doing it, because all the people who have quit with still a will to race have regretted the decision.
"I'd like to always maintain this life style but also race and try to go quick."