- what do you do while you're compiling?
OR
- What could I do in short bursts such as this to improve myself?
If it's the link time that is taking that long then consider splitting the projects up into DLLs so that it's reduced or eliminated. (I assume you're on windows because you said Solution, which means MSVC)
If it's just taking that long to compile, then consider using less templates, more forward declares, less headers being included in headers. Precompiled headers are a must too.
If all that has been done then consider using a distributed build system, there are many out there from Incredibuild, proprietary stuff from Sony, fastbuild, or other open source solutions.
Then there's also unity builds, but I despise them because they effectively break certain forms of file based encapsulation.
I also keep a running list of stuff that I need to get done that isn't dead urgent ("write up ticket about feature X" or "check with Bob to confirm that customer was satisfied with solution to Y"). I can usually knock out a few of those when waiting for compilation or similarly slow blocking tasks (in my current stack, that's running database migrations).