PhD in Biology: how time consuming?
The answer is, of course, that it depends. If you're in the US the first two years are functionally two jobs - classes &amp; candidacy, and research. I think most people end up working a lot. If you're continuing in the same program as your masters degree it will be less time consuming because you've already knocked off your course load, but it's not going to be much better than what you've already experienced.
It's also very PI dependant. Some PIs will be fine with something close to a 9-5. Others will expect an 80 hour a week workload. You should be careful with who you choose to work for. I would advise looking for associate or recently promoted full professors with children under the age of 15. Labs which are entirely international students are a red flag. There's no replacement for talking to current students in an informal capacity about work life balance. Spending $20 and a night at the department happy hour is an investment that will pay off when you pump people for information.
FWIW I did 60 hours a week through my PhD but got much better at time management and got that down to 40 a week for my postdoc. It is doable.