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I generally disable all caching until my site is all set up, tweaked, fine tuned, and ready to go. Caching is great for speed improvements (particularily in areas of your site that you may only update once a month for example) but irritating when applied to areas that are updated frequently or are dynamic by their nature (for example, discussion forums).
Templates_c only need to be emptied (apart from the index.html file) when you have made changes to a module or when you have upgraded part or all of your site. Often, if you don't refresh it, changes won't always show.
But, once you have your site set up, and in between upgrades, the folder does not need emptying and you can tunr the 'update templates bla blah blah...' in system preferences to 'No' as opposed to 'Yes'.
Ted