fs events do not scale on linux, at least not with the inotify facility as watching directories is not recursive and watching large trees, e.g. for creations, modifications or removals .htaccess, will essentially require you to have an additional watch descriptor per directory, and there are limits on number of queued events as well as number of watch descriptors per user. The alternate fanotify has it's own set of drawbacks, such as the need for CAP_ADMIN. Not to mention the mess you may get in when you're trying to monitor certain file systems, especially certain network-attached ones.

Other operating systems have drawbacks as well.

It's probably a safer and maybe even more efficient bet to just do the stats and opens and hope that the kernel/OS file system caches will save the day. Or you can go the nginx route and not support .htaccess like facilities (e.g. turn if off in apache).