How many browsers have you tried? Firefox regularly runs for a long time on my machine, and I have no issues with its memory usage.
It seems to be difficult to generalize about these things. Someone will say that a particular version of a browser leaks memory, or pegs the CPU, and someone else will say that the same version has no problems.
FWIW that's indeed my experience with qutebrowser as well. Everyone seems to have rather different experiences (or expectations?) when it comes to performance and RAM usage. Doesn't exactly make it easier to track issues down, unfortunately.