I found with FF on my 512Mb ASUS Netbook I regularly had to blow away the cache, sometimes I even had to blow away those sqlite files too as they seemed to bloat up to 60Mb with zero cache.
There was also this FF option of looking for search engine updates which needed disabling. Plus disabling the check to see if FF was the default browser, disabling checking for FF updates, disabling FF cloud (or whatever they call it, sync I think) all of which added to the overall FF start up time.