Also, number 2 REALLY shines when you have concatenated items such as scripts together, so you just check the expiration of "all-the-scripts.js", and only load

Also, number 2 REALLY shines when you have concatenated items such as scripts together, so you just check the expiration of "all-the-scripts.js", and only load it once. (apologies to those who already mentioned concatenation, but I thought it worth mentioning what a bonus "cache headers PLUS concatenation" is)