Qatar MotoGP, Doha
Date: 11-12 April
Saturday 11 April: Qualifying: BBC Red Button and BBC Sport website - 1950-2300 BST Sunday 12 April: Preview -BBC2 1300-1330 BST; 125cc and 250cc races - BBC Red Button and BBC Sport website 1750-2005 BST; MotoGP race - BBC Three and BBC Sport website, 2045-2200 BST
Rossi is looking for a ninth world title in all classes in 2009
Valentino Rossi says he will keep riding in MotoGP as long as he still has the incentive to win.
The Fiat Yamaha rider regained his title in 2008 after a two-year gap and begins his defence in Qatar this weekend, two months after turning 30.
Italian Rossi revealed: "When I start to feel less fast then that is the time to stop.
"But I have a two-year contract so I have to stay concentrated and give the maximum to stay at the top."
Rossi has won five out of seven world titles contested in the MotoGP era and eight world crowns in all classes of the series.
Last year he beat defending champion Casey Stoner in what turned into a two-horse race for the title but he said rule changes and the talent of his rivals, including team-mate Jorge Lorenzo, Dani Pedrosa and Stoner, should make for a more open campaign this time around.
"I'm the older generation for sure but I feel strong like when I was 22," he insisted.
"At the moment maybe me and Casey are faster but it's not a situation that arrives at the end of the season.
"Every year I have to work harder. I'm older than my principal rival but I'm not old - mentally and physically I'm in good condition so I'm ready for the championship.
"Last year I had incredible motivation to show I was at the top, now for this year I have to find new motivation to stay there."
MotoGP has felt the credit crunch as much as any other sport, with Kawasaki being forced to withdraw from the 2009 championship and new restrictions on testing and development time being introduced to keep costs down.
Rossi believes this could introduce an element of unpredictability into the title battle.
Stoner (left) was Rossi's main rival in the 2008 championship
"We were used to improving the bike in the season a lot in the past, with nine or 10 tests during the season and also sometimes on Monday or Tuesday on the race track," he said.
"Sometimes it's possible to fix the problems - now if you have a problem at the start it will be more difficult."
He also thinks the lack of testing time may place greater importance on past experience, thereby counting against younger riders.
"I remember when I started in the winter of 1999-2000 I did a lot of kilometres through the season and that's now disappeared," revealed Rossi.
"For young riders, it will become more difficult and it becomes more important the experience that everybody already has."
He also warned that the reduced track time may result in an unpleasant side-effect for some riders.
"With only a few hours on Saturday it will be nearly impossible to make a good setting for the race and as we don't practice on Friday, there will be more dirt on the track for the race and less grip and more danger," he stated.