This is a difficult question to answer as each parking operator will allow different grace periods to purchase the desired parking session. We would always urge you to make payment with the RingGo parking service immediately upon parking and do not delay payment until boarding a train or arriving at work, etc.
The RingGo parking service operates in the same way as the on-site payment machines so it should be assumed that your parking will be paid for within 5 to 10 minutes (maximum) after arrival (i.e. the time it takes you to walk to the payment machine, purchase a ticket and return to your vehicle). These rules are no different with RingGo!