The important thing to ask about code that you "find" is, "What does this code actually do?"
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
The answer is that it invokes
two calls in a row to the operating system on your server to check the filesystem --and possibly to go read the physical disk--
for each and every HTTP request that arrives at your server.
As such, it is slow, wastes energy, and may indeed wear out your disk three times faster than normal...
There are usually much much better ways to do what you want without checking the disk for file- and directory-exists all the time. A static exclusion for common image, CSS, JavaScript, document, and multimedia filetypes is usually much to be preferred.... For example:
RewriteCond !^\.(php|gif|jpe?g|png|ico|css|js|xml|pdf|doc|wav|mp[34]|swf|flv|mov|avi|wmv)$
adjusted to suit...
Even if 'exists checks' are actually required, preceding them with this (or a similar) exclusion is almost always possible -- and a very good idea.
Jim