i've played a little using precompiled headers with gcc,
it works, but the effort is high, especially if you have so much modules in use like C:B has
and the gain is low, because the most time is consumed by the terrible slow linker.
the only solution i really can think of is to use a faster compiler like
DigitalMarsCompiler (DMC, fastest of all) or M$VC
the drawback is, both DMC and M$VC, are lacking a good usable debugger in the free-versions.
on the other hand, a DMC-CD with IDDE only costs 45$
i've ordered one after playing a while with the free version,
and i will switch over to DMC for my future projects.