I usually get around the CPU limits by running 2 sessions..... For instance You have one session for Drums, Bass, Keys, and other stuff... and then one session for Guitars and Vocals....
For instance, start the bed tracks of your song in a session, and when your getting close to running out of power, do a summed mono bounce of a rough mix.... then import that mix into a new session.... Start recording more stuff in that session......
Then you have 2 seperate sessions.... All you have to do to get them together is, do a final bed track mix back in your "bed track session", and bounce it to disk in stereo interleaved format.... Then do the same with all your vocals and guitar.... Now you have 2 stereo wav files....one of Bed Tracks and one of Guitars and Vocals.... Import them both into a new session and you might need to line them up by sliding them around, which is simple.....
I know what your gonna ask next.. "What do I do if the mix is off"..... Well that's simple
For instance if you find that the cymbals are too loud, or say your keys are too loud, just go back into THAT session and fix it and rebounce an updated mix into your master session.....
It sounds really complicated, but it's so simple, and I do all my stuff this way...... I run waves also... and I use about 50-75 tracks in some of my songs.... this is a very good way to do it... Run a bunch of smaller sessions instead of one packed to the tit's session...
Joe