Versons 9 - 11 driving me nuts

Question

First, I don't expect any help. I'm simply putting this out for comment.
I love Firefox. I depend on it to do my work. But since upgrading to version 9, it has become increasingly frustrating to use.
First, with each new version it has gotten slower. I don't expect it to be as fast as Chrome. I have dozens of addons & a huge bookmark file for Firefox. Chrome consists of the bare essentials. But I don't expect Firefox to spend 30 seconds loading a page vs. 2 seconds for Chrome.
The speed problem does not seem to be site specific or related to how many tabs I open at once (I generally open 3-5 at once repeatedly). But after 15 or 30 seconds of waiting, I can switch to Chrome, open the same page (or pages) and they will load at once. Well, actually, two web sites have become almost impossible (speed-wise) to use with Firefox and for those I routinely turn to Chrome now.
Crashes. With each version since 9, Firefox has crashed more and more and more. Sometimes as much as 4-5 times in a single hour. It can crash right after loading, on web pages that contain almost nothing but text, when a single tab is open or when multiple tabs are open.
I have not added any extensions or plug-ins since Version 9, alhtough I have kept them all up-to-date.
When the crashes started, I did disable all but the most crucial extensions in an effort to identify a potential villain, but it made no difference.
Running in safe mode is not a practical option. I use Firefox for work. I need the extensions for work. And since the crashes are intermittent and follow no pattern (I can work for hours without a single crash or get 5 crashes within the first hour of turning on the computer), running in safe mode wouldn't prove much.
I have submitted all the crash reports.
I don't know what else to say except that I am extremely disappointed. ( I'm even using Silk and Opera on my Kindle Fire over Firefox because they each do one or more things better than Firefox which does nothing better than either. I mention this only because it is making me wonder about the entire development process, desktop and mobile).
Bottom line: I seem to be adding more and more web pages of sites I must visit daily to Chrome and putting up with all its limitations because it is fast and reliable. IOW, I'm starting to make Chrome my primary browser and Firefox my secondary browser, for use only with those sites or situations where I aboslutely must use one of Firefox's extensions.

Answer 1

Thank you for your offer of help.
I understand the difficulty of fixing problems like this, which are intermittent. The issue for me is that I'm not doing anything different from what I've done almost since I started using Firefox (ver. 1). I have certainly not changed anything significant in the past 6 months. IOW, I have not added any new extensions or plugins - although I have upgraded them all as I have upgraded Windows (x64) regularly.
I do use multiple profiles for different versions of Firefox - specifically to deal with upgrade issues - but since this problem has now spanned 3 versions, well, that's not an option anymore.
I am guessing that there is some kind of memory problem since Firefox has occasionally crashed right after loading - or even when I'm not doing anything with it, just sitting on a page.
One other thing re the page retrieval. Sometimes, when a page is taking forever to start loading, if I stop the load then restart it, the page will be retrieved. I've tried Y-Slow, but it can't see anything until something starts to load and the problem is that nothing is getting retrieved for Y-Slow to see.
The one constant seems to be that once I have had a crash, more crashes will follow. After a crash, I will clear the disk cache. I've tried intermittently clearing the memory and disk caches to prevent a crash. Doesn't seem to help. (I suspect it might help to reboot the computer after a Firefox crash to get back to some pristine point but that's about a five minute process which would just add to the disruption.)
I almost always have 1-4 applications open when I am using Firefox. They are the same applications I have always used and don't think any have been upgraded in years. I've tried loading Firefox before I load anything else. I've tried loading Firefox after I've loaded everything else. Neither option seems to make a difference.
The max open apps: Lotus Word Pro 9.1, Word 2000, Notepad++ (up to date), WinSCP. Don't ask. I have reasons for using these particular applications.
The worst web sites, where I am now using Chrome:
http://www.caracoltv.com/producciones [open tabs come from a selection on this page]
http://rederecord.r7.com/ [open tabs come from a selection of programs]
Both are sites where I routinely open 3-5 tabs at once. Note again. I have been doing this for a long time with multiple versions of Firefox. Chrome handles the 3-5 tabs with no problem. But since Firefox 9.1, even loading one tab from either of these sites in Firefox can take longer than loading 5 tabs. Yes, the pages I'm loading are full of graphics and or video but Firefox used to handle them with little trouble.