that is the best way to solve the problem - always off by default is better than being required to remember that one must disable something unwanted.
that is the worst way to solve the problem - just use incognito mode.
I disabled the disk and memory cache in Firefox a couple of years ago. Don't knock it until you've tried it. It has much less of a performance impact than you would imagine. I have an 8Mbit internet connection, YMMV.