I never let a new version spoil my addons. That's why, I install Nightly Tester Tools
when I take a look at a new version.
And, of course, I don't allow new versions to replace existing one. I have, presently, three different versions of Firefox, installed in different directories, and with their own profile. They mind their own business, and I will keep them as long as they don't bother me.
UserAgent: Mozilla/5.0 (Windows NT 5.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1
A minority may be right, and a majority is always wrong
~ Henrik Ibsen
WinXP, SP3, 512 MB, SM2.17.1, FF21, TB17.O.5, IE8.0, Google Chrome 27, Ghostwall , Avast 8.0.1, JRE1.7_21.