"Getting that JavaScript is a one-time operation, and a 304 from then on." In theory it sounds right. However, there are a couple of cases where users will hav

"Getting that JavaScript is a one-time operation, and a 304 from then on." In theory it sounds right. However, there are a couple of cases where users will have to load JS a lot more than they should. Since most of the logic lives in the JS file(s) they will be changed and pushed out a lot more. This will force users to download the JS every time code is deployed. Also, I am not sure what percent of "New users" land on Twitter pages, but they will have to download the JS.