They definitely pitch less. The belief is that when a pitcher begins to tire, they stop using proper mechanics to compensate, so the biggest injury risk is pitching while tired. They now count the number of pitches thrown and pull a starter quickly when they're near a predetermined maximum. They used to view off-days as chances to skip the worst pitcher in the rotation and start the best pitcher sooner, but now it's generally an opportunity to give every starter in the rotation an extra day of rest. And they now put pitchers on the disabled list at the slightest indication of a problem. But are Verlander and Scherzer's dominance at an older age a result of that?

It's hard to say.

There have always been occasional pitchers who are still effective at an old age. Just from my lifetime, Perry, Kaat, Sutton, Niekro, Ryan, Clemens, Wells, Johnson, Moyer, Colon come to mind. Scherzer and Verlander are just two guys and not a representative sample of anything and could just be random chance, and they're not even that old yet. 37 and 39, while Perry and Clemens won Cy Young awards in their 40s, Ryan lead the league in strikeouts at 43, Colon was an All-Star at 43, and Niekro was an All-Star at 45. And for all the talk of Scherzer still pitching well at 37 and Verlander winning the Cy at 39, it's still a young man's game. The top 7 finishers in the NL Cy Young vote were all in their 20s, and 2nd through 8th place in the AL were also in their 20s. The young are still dominating, and being a good, old pitcher still makes you an outlier.

And even if we could say for sure that pitchers are aging better, there are lots of potential explanations: pitch counts, extra rest, improved medicine, something nefarious like PEDs, or I once read a study when Clemens and Wells were still going in their 40s suggesting that fat pitchers age the best and it successfully predicted Bartolo Colon's longevity (and while neither is fat, Verlander definitely looks heavier than when he was young).

Less, like a lot less. Probably 25% less for a starting pitcher. It's rare for a pitcher to pitch into the seventh inning now.