there's a real open question regarding app downtime. I know being 'on call' is a common occurrence in a number of tech positions, but if the thing really 'needs' to be responsive and up 24 hours VA day 7 days a week and something can explode and take it down, then one should probably look at what other sectors with that kind of need do and have rotating shift/ rosters...

course, that would probably result in lower wages for those shift

(that being said, in my country, doctors working hours in the likes of hospitals are notoriously unsafe/long/unreasonable/unethical as well, so your mileage may vary)