Firefox Night (23.01 64bit) can run for days without becoming sluggish (longest I ran it is for about 2 weeks).
Most recent build however tends to crash on something (still trying to figure what it is, but it seems rare and they are patching ... nightly reducing it more).
Do love the noscript!
I tried chromes noscripts but that... doesn't work as well ;/
P.S. averaging 5 windows and 80+ tabs during usage (left open that entire time) browsing several hundred megs/several gigs per day used about 2GB ram before I restarted it (last stable nightly I used anyway)
XI Wiki



