Two of the more expensive parts of cooking for another platform are compressing the textures in a platform-specific format and generating/compiling shaders for materials. We store the results of these steps in something called the Derived Data Cache (DDC), which lets subsequent cooks do less work if the assets haven’t changed. However, the first time you cook for a platform, this can take a decent amount of time, especially if you are doing all texture formats for Android instead of just ETC1. In most cases I’d recommend doing just ETC1, as it’ll take less time and generate a smaller APK that will transfer/install faster as well.
One other gotcha (which shouldn’t affect most people in practice) is that we flush entries older than 34 days from the DDC, so if you don’t work on a project for a few months and then come back to it, you might have one slow cook before it’s speedier again.
Cheers,
Michael Noland