It’s about 5 times longer than previous releases were maintained for, and is an experiment. If there’s a need for a longer term support branch, there will be one. It’s pointless to start maintaining an 5+ year branch with 0 users and a handful of volunteers, none of whom are paid for doing the maintenance.
So yes, in that context, 15 months is long.
Yes, Forgejo has integrated CI/CD. The Forgejo project itself uses it aswell, quite heavily. It is… somewhat compatible with GitHub actions, but not completely, and it will never achieve feature parity. It’s an okay CI/CD system though, not worse than all the rest, and has the advantage over all others that its integration with Forgejo is tighter.