Sure does; I think it has to do w/ deallocating memory on closing of tabs [or navigating away]... flash-player and other such plugins might also be culpable.
I leave it up until about 80% of my memory is used up, then have to restart it.
I haven’t been on any machines with less than 6 GB of RAM in several years, so I guess I never noticed.
It does depend on extensions, plugins, O/S and possibly other factors. My old laptops are 512 MB machines; I hibernate and wake them all the time with only rare reboots. Firefox memory goes up and down but does not trend up.