Every developer should be forced to tech support at some point. And additionally sales calls. While I really hated doing the latter it gave me some appreciation to what they have to do. Customer support gives you insight into how your actual customer used your service and their pain points. It's incredibly valuable as developer to see that point of view directly.
Absolutely agreed! A while back I gave a talk on why everybody should do support: https://vimeo.com/136270620
I coached for a long time at a weekend workshop called Lean Startup Machine and it was amazing how much teams would benefit from just talking with 5-10 potential users. They'd often come back in a few hours and say, "Ok, our previously brilliant idea turned out to be entirely dumb, because we didn't understand X, Y, and Z about our users. Let's try this again."