I know the auth issue exists for several people... And I don't know the steps to change that.
But, I have my desktop PC logged into (2 factor) Gitlab, and almost never need to re-login (once a year on avg, but some even further appart). Even, if I was away for some days. I don't know why that does not work for others.
It persists (on the main browser) even if I open a 2nd session with the same account in a diff browser. (IIRC, I don't do that often).
I use Firefox, but I don't think its bound to that....
To view bugs I have a little grease-monkey snippet showing me several lists (created, updated, closed, assigned) like mantis used to.
Bit of a hack though, using css from the original gitlab side, means it needs occasional updates.
And cross page rules mean, I have to fake it into the gitlab domain.