Every one-time purchase extends the validity period of your Premium access by the period of time your purchased for the package you selected.
An example of purchasing Premium access for the same platform:
1. You have an active package:
Web + Android with Premium access expiring on 30 June 2019.
2. You purchase another package:
Web + Android for three months
Result:
The validity period of the Premium access for this package (web + Android) will be extended to 30 September 2019.
An example of purchasing Premium access for another platform:
1. You have an active package:
Web + Android with Premium access expiring on 30 June 2019
2. You purchase another package:
Web + iOS for three months
Result:
The validity period of the Premium access remains without change (30 June 2019), but your Premium access will be extended to the iOS platform.