I think it is possible to win a lot of tournaments in one year but as BobbyOne mentioned in the post above me, players like Federer tend to focus on the majors nowadays. Look what Federer recently said, he basically said that he wanted to limit his schedule to get ready for the next Olympics in what I assume he hopes to win the Gold Medal. The players in the past, even the recent past like the Borg era focused not on the classic majors, which were important but not the end all that it is now. Borg for example won 21 tournaments in 1979 and he obviously entered a decent amount of tournaments that year. I think Laver entered about 37 tournaments one year and remember they also played doubles in those days! Federer for example from 2004 to 2012 never entered more than 19 tournaments in a year and he played as few as 15 in 2005 and 2009. A player is far more rested and less prone to injury. It's a smart thing to do. The players today don't have to worry about the monetary aspect because they are set for life. Players in the past had to be more concerned about money. Yes I do think it is possible to win a lot of tournaments but they don't have to and why should they?