Pre HRT, starting with childhood, I also had a tendency for nightly cramps in the legs, or worse yet, the feet. One big cause was icy cold feet (Raynaud's Syndrome), and perhaps some dehydration. I've never been a big water drinker.
Post-HRT I can't say it's been much different. Yes, more sensitive and aware of dehydration. (After another 50 some odd years you tend to be more "aware" of it compared to as a kid). I also notice a very tight correlation to peanut eating at night and severe cramps.
BTW - there is an amazing homeopathic instant cure for leg cramps that works for me, it is made by Hyland's. Pop one or two under your tongue in in seconds the cramps are gone! I've been using it for decades