I mean if we're going by specifics... a long hard fought tennis match will go about 60-70 games inbetween both. These guys are on pace to be done at around 150 games....
Thats essentially a 20 inning game in baseball... which do happen once a season or so (maybe not as much in the past, but that seems to be happening more now)
I guess in baseball you're also standing around or sitting, and you're constantly moving in tennis...
Remarkable though... it was by far the best sports day of the year so far, and one of the best overall days for Americans outside of the olympics... probably ever.