How long may I stay out of UAE in order to keep my resident visa valid?

If your visa status is Investor, you are allowed to stay out of UAE 12 months and enter UAE every 365 days in order to maintain your visa. 

If your visa status is other than Investor, you have to enter UAE every 6 months to keep the visa valid.

In case you fail to come or overstay abroad, your visa will be cancelled automatically and you will need to apply for a new one.