Hmmm, I've cramped 3-4 times I can remember in crazy long grinding 4.5 matches. Once in Tuscon AZ. Everytime I've finished the match, usually win the match, maybe I should try to cramp more because i seem to win those ones lol. Usually down a pedialyte/gatorade/nuun/coconut water and play crazy aggressive until it goes away. One match I felt twangs of a cramp but hid it from my cramping opponent, when I went to shake hands at the net my entire lower body locked up and i dropped to the ground. He thought I was making fun of him, lol. I'm like, nooo way man, that's some crazy intense pain.
I had a match this year in 110 degree heat against a known super grinder and felt cramps coming on in my calves. Downed 3 oz of pickle juice and it went away. So now that I know that trick I'm not sure cramps will be an issue for me again.
Also to add, I've never seen someone default a match because of cramps at 4.5/5.0. We're usually all good athletes and know how to hydrate properly, if you're dehyrdrated I think that's a better reason to default a match, especially if its crazy hot.