The validity period will depend on the number of zones selected. The more zones covered, the longer the card is valid for. For example, a Mobilis 1- or 2-zone ticket will allow you to travel for 60 minutes from the time of purchase, whereas an 11-zone or higher ticket will let you travel for 4 hours. The validity period is printed on the ticket.
While the ticket is valid, you are free to use all public transport lines located in the selected zones as many times as you wish. However, you must make sure your ticket will still be valid by the time you reach your destination.