Perpetual license (purchased license)
Perpetual license is a one-time-fee purchase. Once purchased, it can be used for an unlimited period of time for an exact Plesk version.
SUS is required in order to upgrade such licenses.
Plesk perpetual licenses are updated once in 1 month. Details are available here.
Currently perpetual licenses are not available for purchase, existing licenses remain active.
Lease licenses are paid on monthly or yearly basis and are valid while they are paid for. Otherwise, lease licenses expire.
We recommend you to keep track of your billing account (expiration date, available balance, validation) and inform Plesk Licensing and Purchase Support if any changes were performed.