Yeah but it's mainly about desire to play, IMHO.
I feel like I've been hearing "Nadal's playing style won't last long" type of comments for like last 10 - 15 years.
People still saying same shiiiit even right at this moment now, after all these friggging years.
For career as top 10 or better and winning slams, Nadal seems to have almost same career length as Federer's (or he could last longer in the future, no ??)
No, the comments about the effects of Rafa's playing style on his body are not BS at all. They are on the mark as evidenced by the number of slams, masters events and other tournaments he has missed.
Sure, Roger has been taking some time off since his mid 30s to recover. But if you consider events missed up to the age of 30 or so, Rafa has been injured and missed matches quite a bit more than Roger (even tho Roger has been plagued with back problems and a bit of mono since his teens).
Rafa started playing a full schedule late in 2004 and won his first RG in 2005. Since 2006, Rafa has completely missed (not entered) the slams a total of
6 times. Since 2005, he has skipped Masters tournaments some
24 times. Rafa has missed or skipped lesser events quite a bit as well.
Rafa has been injured and missed major events in 2006, 2009, 2012, 2013, 2014 and 2016. He also had a significant lull in his career from late 2014 thru the end of 2016. Since AO 2017, Rafa has made a resurgence. It will be interesting to see if he can remain relatively injury-free in 2020.
In his mid/late 20s or so, Rafa (along with Uncle T, Carlos Moya and his other coaches) have come to fully realize that Rafa's playing style was taking its toll on his body and adjustments needed to be taken. He and his team have made adjustments in his training and taken a number of counter-measures to minimize the effects of his playing style on his body.
Along with changes in his workouts, Rafa undoubtedly engages in a fair amount of physical therapy, massages and other measures to aid in his recovery and minimize injuries and other effects of his playing style. It is well known that Novak has used a specialized Hyperbaric Egg for his training and to aid in his recovery. I suspect that Rafa has also spent quite a bit of money & time for his own training and recovery. Without these extra measures, Rafa might have very well retired in 2015 or 2016 as many had predicted or expected.