You can limit the write actions of Firefox as follows.
a. Set the cache to 0: Firefox menu button (with the three dashes on it) - Preferences - Advanced Tab Network section "Cached Web Content": tick Override automatic cache management and set the cache to 0 MB.
b. Type "about:config" in the url bar and press Enter. Click the button to accept the risk.
In the search bar, type: "sessionstore"
Double-click on the item called "browser.sessionstore.interval". The default interval is 15000, which means 15 seconds. Add three zeros to the existing value, so that it becomes: 15000000 and click the OK button.
Now disable the following three other sessionstore items, by simply double-clicking them (so that "true" becomes "false"):
browser.sessionstore.restore_on_demand
and:
browser.sessionstore.resume_from_crash
and:
services.sync.prefs.sync.browser.sessionstore.restore_on_demand
Close Firefox and launch it again. Now you've disabled the session restore feature, which remembers what pages were opened if Firefox experiences an unexpected shutdown (read: crashes). This feature is neat, but causes many disk writes. Too many for an SSD.
c. If you have installed Oracle Java, limit the write actions of the Java plugin: launch the Java Control Panel - Tab General: Temporary Internet Files - Settings... Remove the tick for: Keep temporary files on my computer.