i call a 'job' something that has a stable job description, clear career path and predictable roadmap. vacation becomes just another item on the calendar then, which is perfectly fine.
you can and should still excel in those conditions, but the project won't be jeopardized or stalled if you take time off. and when you come back, chances are that the specs of your project didn't shift yet.
there is a surprising amount of people working in jobs, even in technology sector, but they are not founders or employees of early stage companies.
and yes, if you feel like you need time off, you need time off. but planned vacations in this environment I just don't see plausible. I've never been able to even book a plane ticket more than a week in advance, because plans always changed.
best, b