General :: Relocating Firefox Cache To RAM Not Working?

Firefox has this nasty habit of wanting to write to disk just as it's spinning down when I'm on battery...this is of course annoying because it'll probably shorten the life of the disk (it's doing it as I type this post!)

I figured that a solution to that would be to set FF's cache to be in a RAM disk instead of on the hard disk, so I tried following this guide on the Arch Wiki to set it up (the "Relocating only the cache" section). I followed it to the T, and it did nothing to change FF's disk usage. I even tried adding a /tmp entry in /etc/fstab that would supposedly mount /tmp on a RAM disk and pointed FF's cache to that...still no cigar.

My /etc/fstab:

Code:
#
# /etc/fstab: static file system information
#
# <file system> <dir> <type> <options> <dump> <pass>
devpts /dev/pts devpts defaults 0 0

[Code]....

What is it that I'm missing here? Is my fstab incorrect? Is there something else I need to do in FF? I've searched Google and LQ about this issue and couldn't find anything other than the same instructions found on the Arch Wiki and the /tmp fstab entry idea.