I once implemented caching middleware complete with logging of request times so we could see which calls would benefit the most from caching. We never turned it on. A few months later our system is on fire so the investors send a guy to babysit us and improve things. He starts writing a profiling tool. He won't listen when I tell him that I've already done it, just ignores me. I got so frustrated that I log into the production system and turn it on manually for about a minute. Email him the resulting log. He makes a histogram in excel (doesn't mention me) and there was much rejoicing. (And we started caching requests and lo, the servers did cool.)