I did 3 back-to-back-to-back JFK - SFO MRs in April 2021 ($400 total lol) to reach 75k (and eventually 100k it turned out). Still took the subway into town each night for about 6 hrs proper rest. Definitely wouldn’t do it again, esp if it required sleeping at the airport… granted if there’s one airport in the country to sleep at, SFO is it