We don’t have any use-time guidelines and nothing can be guaranteed. That said, there’s no reason it shouldn’t be able to run continuously if you don’t let it get too hot - i.e. don’t put it in a cupboard with no airflow.
It’s not advised to have the board directly accessible from the internet. The SSH and Jupyter passwords are well documented so at the very least you should change them from the default. I’d also recommend having it only accessible from a private network as Jupyter has direct root access on the board. We’ve been using a ZCU104 and a Z2 like this while working from home.
If you’re not going to have easy access to the board I recommend researching how to turn on the watchdog timers available in both Zynq-7000 and ZU+. They will reboot the board automatically if it locks up which makes life a lot easier when developing.