Firefox -is- a memory leak, and multiple tabs seems to aggravate the situation.
I know. :(
I am... disappointed with the quality of "acceptable" software, being a programmer myself.
You are correct, and sometimes the CPU will be up around 50% continually after coming out of stand by. And so i use Process Explorer to restart it and then it is OK, plus Session Manager saves multiple sessions well.
For me there has been no substitute for FF with the speed i still get having tabs all before me, plus other features. Chrome does not even do multiple rows, and besides other things, the width of tabs in Opera cannot be reduced to anything close to what i do in Firefox and ID them well. Thank God for all such wonderful tools!