Depends on what they do with those 30 and 50 hours. If they're burnt out, even 100 hours chained to an in-person desk, they aren't going to accomplish much, so that's just not true. The right software engineer can come in, have a pointed discussion, have some coffee, go look at some code, have a few conversations, and have a bigger impact in an hour in terms of setting future direction and avoiding pitfalls than a different engineer could do in a week.