My 80's cover band plays several songs that fade out at the end of the tune, which can be a challenge when performing live.
How do you end songs that fade out the end?
IMO you do what bands have done for decades and decades - make up an ending!.
Certainly don't fall into the trap of thinking that just because the record fades out, your audience expects it to fade out.
When a record starts to fade out - that's the cue for DJ's and radio stations to move on to just song.... not ride that fade to the end.
And when live bands try it - it has an even worse effect. Imagine the party's jumping - the dance floor is full of energy - then the band decides slowly turn down the energy gradually over 30 seconds... or more.... Why? Are they done? Are they leading to a ballad? A fade out just screams "Hey everybody - Calm down..."
My suggestion - keep that energy up - hit them with definite ending - so they can go "Wow, that was great" - and then go into the next song. No dips in energy/vibe - for no good reason.
What to do for endings? Up to your band.... make them as simple or unique as you desire. But millions of songs have ended by cover bands hitting and sustaining the last root chord. Or finding that obvious place to stop with a short hit.
Heck I've played hundreds of weddings where the leader just cued these with gestures on-the-fly. Try and escape the mentality that your number one job as a band is to faithfully recreate records. Even good DJ's that simply playing records knows that's not the main job. The main job is to serve your audience.... insure that they have a good time.
Be creative and make up endings. And if you are searching for ideas - don't go looking for the answers to your specific songs - just watch a bunch of concert videos and see what those bands do to their songs - then just apply those basic ideas to whatever songs you are doing. It's really not that complicated - there really is no getting this wrong - just give yourself the license to do it.... and then just well... do it.