When you purchase any Kentico CMS license you get the maintenance for 1 year included. After the first year, you can renew the maintenance or keep using the license without maintenance. The maintenance period starts from the date when your last maintenance period expired.
The maintenance covers:
free technical support during the maintenance period
free major upgrades (6.0, 7.0, etc.) released during the maintenance period
See the maintenance renewal prices
Maintenance Renewal Process and Late Renewals
The customers receive a notification of expiration 2 months ahead, 1 month ahead and at the time of expiration. Then, they have 30 days to renew their maintenance. After then, the maintenance renewal costs 50% more. The example below illustrates the process: