I only use chrome for anything related to Google such as access to "my drive", hootsuite app and "google my business". Otherwise its the modded FF for me.

I never get logged out of this site... never. I, as an old gamer have nothing deleting cookies, cleaning anything or updating anything automatically. In fact honestly I rarely worry about cookies.

Check if your chrome browser has a setting to clear cookies periodically and if it does turn it off or see if there is a place to whitelist the cookies which store logins for frequently used sites such as UU.

Good Luck