MELBOURNE - Roger Federer has no idea how long he will continue playing competitive tennis after winning his third Grand Slam title in a year at the Australian Open on Sunday.

The 36-year-old Swiss marvel continues to defy the years and attrition rate, reaching his 30th Grand Slam final en route to claiming his sixth Aussie Open crown and 20th Grand Slam title.

The world No 2 won back-to-back Australian Opens by beating Croatia's Marin Cilic 6-2, 6-7 (5), 6-3, 3-6, 6-1, dropping his only sets of a stress-free tournament.

Federer, who downed great rival Rafael Nadal in a classic five-set Australian final last year, eased through this year's event with five of his seven matches finishing in under two hours, and he spent just a total of 13 hours and 53 minutes on the court.

Asked after his Melbourne triumph how much longer he can continue at the summit of men's tennis, he replied: "No idea. Honest, I don't know. I have no idea.

"I've won three Slams now in 12 months. I can't believe it myself. I've just got to keep a good schedule, stay hungry, then maybe good things will happen."

Federer said his age didn't come into it when questions were raised about his continuing longevity.

"I don't think age is an issue, it's just a number," he said. "But I need to be very careful in my planning, really decide beforehand what are my goals, what are my priorities.

"I think that's what's going to dictate how successful I will be.

"I see exciting times ahead. As a professional, it's what we do. But I'm happy I'm in that position right now."