Some publishers offer extended access to their content: you have continued access after leaving, the college's IP address ranges, depending on the publisher the connection hours also differ.
How to use it?
Elsevier (ScienceDirect) for up to 48 hours.
American Chemical Society (ACS) for up to 4 months by pairing your account, you can follow the publishers instructions here: Pair Your Active Subscription (acs.org).
Wiley Online Library for up to 60 days.
Springer provides “Persisted authentication” up to 180 days after users’ last institutional access.