There's a lot of "it depends" here. As both a former founder and early startup employee these are the things that come to mind— How far out did you discuss this with your employer? Were they aware of it when you joined? There's a pretty big difference if this is 6 months or two weeks away. Setting expectations go a long way here on both sides. What is the size of the business? People are more critical the smaller the…
This is unbelievable nonsense. Your employees accrue PTO. If you can't handle them using their PTO, maybe you shouldn't have employees. If three consecutive weeks is a lot to ask, what would you do when that same employee gets hit by a bus and is dead for even longer? Oh right, you'd just replace them and the business would move on. OP, this is the real answer to your question. The business doesn't care about you or…
"Unbelievable nonsense" is a pretty harsh response. If they are working for a 10-person business burning cash, that is very different than a profitable 1,000-person one.
The poster asked about etiquette. Personally, I'd be offended as a founder or employee at a 10-person company if someone asked for 3 weeks off at the last minute.