He hasn't been out of work for 10 years. He hasn't managed a club but he has both served as a technical director and first team coach at Fulham.
He's a bit picky as he's not wanted to take on Championship jobs or relegation fodder in the PL but it's true that he's been somewhat forgotten until recently after leaving Fulham. Could well do a job.
You only really get to see the full potential of a manager when he gets into position of proper power, i.e. money. Big Sam was right in that regard that he never really got the opportunity. After having said that however he messed up the England job and had money at Everton to do something but he failed.
André Villas-Boas is only 40 and should be able to get a top job sometime soon. A year ago he left the money in China.