Does the asset pipeline rails 3.1 waste cycles?

In rails 3.1, does .coffee and //= require files get processed only once or with each asset request?

For example,I have a file

//= require source/main.js.coffee
//= require source/second.js.coffee
//= require source/third.js.coffee

Ideally, the server would compile these to js ONCE, then bundle them, then create a static file. But if it happens on each asset requests,it's going to be wasting cycles repeating it??

Thanks for any guidance on this.