the user library cache...

There is another cache folder as well in the system library folder. They do flush when necessary, but it's best to let the operating system do its thing. Apple don't recommend clearing it, unless you're troubleshooting an application that is behaving in odd ways, like crashing. You can delete the folders yourself, but it will just slow your computer down a bit until the caches rebuild themselves.

If you have a lot of memory available, then Lion will create a temporary RAM disk and keep the cache stuff in there (the copy on your HDD remains of course). This is actually one of the reasons why people keep asking about where their "free" memory is.

 

Very true. People forget that Mac OS X is a UNIX based operating system. With UNIX systems, free ram is wasted ram. Same thing applies to iOS. Just let the operating system do its job.

 

If you've been deleting the cache folder for the past few years, you're probably used to the slower launch times that happen when the caches are deleted. Try leaving it alone, you'll see improved launch speeds.

(You're welcome.)

 

It'll take a few days of uptime before you start to notice any changes. Still, its best practice to leave the caches alone, unless you are told to remove them. Removing them at random can lead to problems, even if you've never seen these problems, they exist.

 

Not deleting the caches is what you're supposed to be doing. Not deleting them won't cause problems unless the application is buggy.

Deleting them without a reason can lead to lost settings, corrupt data, lost activations/licenses, loss of unsaved data, app crashes, increased launch times, unnecessary redownloading/reprocessing of data, and in extreme cases kernel panics.

 

Onyx isn't a very good thing to do. In some cases it can do more harm then good. I tend to avoid it as much as possible.

I've learned all of this by actually looking into what was being written into the caches folder and its general contents. There's also information on the subject in Apple's Developer Documentation.

Saying you've been doing that for years is roughly equivalent to turning off your computer by unplugging it. Sure you can do it, but sooner or later you'll encounter problems.