The 'infinite' lease time is an acceptable vale for dhcp-range and dhcp-host options in dnsmasq, however, it is not possible to configure that via the UI.
Is this something that is intentional or just some temporary limitation?
https://thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html
The issue is that the lease time field in the GUI is an integer field:
https://docs.opnsense.org/development/frontend/models_fieldtypes.html#integerfield
This means only "numbers" are valid.
"infinite" is a text string.
Maybe we could allow "0" and it would set "infinite". For that we need an issue on github:
https://github.com/opnsense/core/issues
Reported an issue upstream: https://github.com/opnsense/core/issues/8671