A break once every 3-4 months if something is due or money is lost is unacceptable. If you can work and set your own deadlines and measure of quality, sure Manjaro will do fine. Ever involved deadlines?

Does Manjaro break a lot?

Software installation on Ubuntu is quick, and things software packages rarely break. Manjaro has a tendency to encounter more breakage as you install & uninstall packages over time, so that you can end up with a system that you can‘t easily install packages on.

Is Manjaro really stable?

From my experience, Manjaro is more stable than Windows. When it comes to updating, you will have to tell it to update, so it won’t automatically restart like window can. The only thing you risk is the computer breaking after an update, so mabey wait to update and look up on forums if the update has broken anything.