BERLIN, Germany - Michael Schumacher, now 43, says age is not a factor in Formula 1 but has left open his future after his 300th GP this coming Sunday.Schumacher told DPA in an interview that age had nothing to do with whether he could win another title if he continues in F1.The seven-times World champion said ahead of Sunday's 2012 Belgian GP that the question of another F1 title "unfortunately is not there" this year, with Mercedes not a contender.NO REGRETS"We are no longer fighting for the World championship. Let's see what the future holds," he said.Schumacher's contract will expire at the end of the 2012 season. He's already said he would like to wait until October before deciding his future.In German media interviews this week he said he had no regrets about his return to F1 with Mercedes in 2010 after a three-year absence though he was still searching for a win. He'll go into Sunday's anniversary ace at Spa-Francorchamps with only one podium place - won from Valencia 2012 - since his F1 return but made it clear he would love to win again."Of course that (failing to win) would be a pity. I would like to experience a highlight or two," he told DPA, "but confirmation of your performance does not only come through victories. I have had a few moments since my comeback which have given me great satisfaction, for example if I can get the very best out of the car, even if it hasn't produced results you can show."That is difficult to explain to the outside because you cannot recognise that from the outside. But the feeling is very nice."'PURE COINCIDENCE'The most recent of Schumacher's 91 GP wins was in China on October 1, 2006, then driving for Ferrari, but on Sunday he'll return to a circuit that's special to him for his 300th race: it's where he raced hiis first GP, where he first won and where he sealed the 2004 F1 title."Somehow everything always seems to play out in Spa - my career circles around Spa, so to speak. That I am now about to take part in my 300th race there is pure coincidence but somehow expected," he said.Win or not, the record World champion says he never stops questioning himself. "Self-doubt is always important. I am always doubting myself," he said. "You have permanently to question yourself to develop and to be able to learn."That's the same everywhere in life." Stay with Wheels24 for the 2012 Belgian F1 weekend.