What's up with Firefox?

I've been using Mozilla browsers for years. I've always hated IE, and as a rule avoid using Microsoft products. I've rarely browsed with IE or received email from Outlook.   I suppose working day in and day out with Microsoft products, I just wanted something different. Also something that has more flexibility. 

Lately I've been finding Firefox absolutely unstable. I run it on my laptop in Windows 7 64 bits, on my home PC in XP, and at work also in XP.  I'm one of them people who never closes their browser, because I live either on Facebook or on my blog, or even on Al Jazeera, for news, Fark for unusual and funny news, and iGoogle, so I get headlines, and my gmail.  That's just my main browser window with all those tabs. Then I have my 2nd, 3rd and 4rth browser windows dedicated to shopping. At the moment I have one window, filled with patterns I want to buy from Jalie, one is filled with about 30 tabs from DealExtreme,  one with Kijiji searches and another with Sony camera lenses. When I launch it with all these tabs opened, it's fine. A few days later, and it's hogging the entire system. 

From my years of experience as a tester, I suspect a memory leak. It crashes about once a day now. I used to be able to run it for about 3 weeks before it became unstable or too large and I'd have to re-start it.  In the past couple of months it's been particularly unstable in XP but was fine in Windows 7. It's this latest version that is flaky as all heck in all Operating systems I've tried.   We've scripted testing of it at work, and on 2 of the 3 machines it was run, it had crashed as well. 

I don't understand why it's so unstable. In the past Mozilla was able to provide us with a quality product. One that was far superior then IE. One that was innovative. The tabs were brilliant and first seen on Firefox. I love the tabs. 

I've also noticed that when I started this blog the majority of the people who read it were using IE, now it's mostly Firefox, and then IE and Chrome usage is about the same, but the two together do not equal Firefox usage. 

So Mozilla, looking forward to a more stable browser in my near future.