Does VENUS and SERENA have the stamina? Yes.
Are they so injury prone that they will probably have shortened seasons? Yes.
I am rather pessimistic about either of them playing in 25 or more events, but I do see them still able to win titles, Grand Slams and stay in the top ten.
Yes and No. Actually it depends on how one defines a YEAR..
Do you mean 23 tourneys or a entire year? Imho alot of ladies on the tour can't play 23 tourneys and stay injury free at all. We all know who they are.. lol
Stamina is really not the problem concerning these two.. V&R. ..(that is) They both played alot of matches and points. Won some huge tourneys and Venus won two slams. Serena made it to a final. Believe it or not.. some players can play 23 tourneys but still not play as much tennis as players who make it to finals and such. Venus just has a delicate body build and her game is hard on her bones and muscles... but as far as Stamina .. that she has.
Venus and Serena have the stamina to play an entire year, and they usually do. They simply play fewer tournaments, and that's because they play well enough to be able to afford to.
The Williams have wonderful stamina when you consider the number of matches they play. For other players, the number of tournaments played sometimes almost equals the number of matches played. In other words, those players make very early exits from tourmanents. On the other hand, the Williams often play nearly through the entire draw, if not win. So whereas Venus only played 13 tournaments, she has 6 titles and almost, if not 30 matches to show for it. Those 30 or so matches are for her wins, she has even more matches under her belt for the tourneys she didn't win.
So yes, the Williams do have the stamina to continue playing an entire year. And they have the titles to prove it.
I would agree that both Venus and Serena have exhibited much stamina during tournaments. Venus beating 3 top 10 players in 48 hours was a great example of this. (I'm sure some Williams fan can come up with the details of that, as I can't quite remember!)
And, frankly, I'm not sure that the question of whether or not either could make it through the year is really relevant. Success in tennis is about working out what kind of schedule suits your body type. Venus seems to have got her schedule sorted - she's able to peak at the right times. Serena should maybe try playing a little more, but I'm sure she's working these things out for herself.
I guess what I'm trying to say is that some players need to play more often than others to keep sharp, others benefit from time off to train. Each to their own.