If I have a VSTi that is eating CPU live, I will route the MIDI track to an audio track, record, turn off the MIDI track (disable) so if I want to change it, I still have it, but I am not using CPU for other live effects.
I have had some VSTi's that really eat CPU and I get an 70-80%+ bounce. Playing straight audio takes very little CPU, it sometimes makes sense to record it and then disable if you are using many voices.