I was wondering if part of your mixing process ever involved converting say a tweaked drum or keyboard midi file  to audio and EQing from there. Is it better to leave the midi files as is when exporting? 

There's no right or wrong. My opinion is that it's a good idea to convert MIDI instrument parts to audio regardless, for two reasons: 1) it's less taxing on the CPU, and 2) you now have an audio backup in case the plug-in becomes unsupported for any reason. But I also archive the MIDI track and save the instrument preset so that if I need to edit later on, it's possible.

Thanks Anderson!!! You made my day!

Oops, there was a hiccup and my response registered twice. Thanks again!

Well, Craig's answer deserved a double-bump ;-) 
 
That's what I do - freeze, copy that to a new audio track and archive the midi track after unfreezing.  Partially habit from when you couldn't run more than one or two VSTi's at once and I just prefer working on all-audio when mixing.  Something about audio waveforms rather than dots seems right.
 
@ 

I always convert before I start to mix. Then I will hide the MIDI tracks and work with the audio only.