Question about cron job scheduled backups

Hello!

I have a question about scheduled backups which use cron jobs. I am aware of the fact that there has to be a visitor in order to the cron job execute. I have a site currently hosted on my local dev server, and I have set up scheduled hourly database and daily full-site backups, and the hourly backup runs only while I am logged in or making anything on the site (so there are site visits/page loads).

My question is: what happens if I set up a daily backup to run with cron jobs, and there is low amount of visits? For example, if I set a daily backup to run at 3 am, if there is a visit only at 9 am, will the backup run at 9, or there are some time limits to that?

Thank You!

http://wordpress.org/plugins/backwpup/