Your compile is taking a while. You check your email while you wait... and then later find you didn't notice when the compile completed.
The best solution is to fix your compile times. (Try splitting your project up into separate assemblies and only compile the ones you are actively developing.)
Failing that, this add-in makes sure you know when the compile completed by displaying "Compiling" in the top left of your window until compilation is complete.
These details are provided for information only. No information here is legal advice and should not be used as such.