There are two things to worry about here: licenses and contracts.
Licenses can either expire or not, contracts always expire at some point.
Most anything outside of Firewall, VPN, Mobile Access, and DLP have a contract associated with the service.
Perpetual features (Firewall, VPN, Mobile Access, DLP) will always function provided there is a valid license and it has not expired (i.e. not a trial license).
All other features will stop working after their contract has expired and all perpetual features will stop working (fail closed) if operating past expiration date.
By "stop working" it means you will not be able to push policies that involve the features with an expired contract and any rules involving said features will not match.
For historical reasons, IPS is a bit different in this regard.
Generally, there is a grace period (60 days) and even after the grace period, a limited set of protections will still be active (all other protections will be inactive).
For the exact behavior, see: https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solut...