How long is a single ticket valid
One zone: 90 minutes from purchase or from when you activate the ticket.
Multiple zones: 180 minutes from purchase or from when you activate the ticket.
How long does pay as you go applies
One zone: 90 minutes from check-in.
Multiple zones: With each check out in a new zone, you get 90 minutes of transfer time. This applies as long as the check-out takes place within 180 min from the first check in.