The rough breakeven time is 42% of the time. If your validator is online more than that you are making money, less than that you lose it. So the protocol is rather forgiving in uptime. That's why it's much better to not run failover of any kind. You can afford to be offline without problems but if your failover fails and you run two instances you get slashed.

There is also a penalty that kicks in if many validators fail at the same time resulting in over 1/3 of the network not being available. In that case penalties are also increased significantly. So if over 1/3 of the network were to be run in AWS those validators would risk heavy penalties if the region were to suffer some downtime.