I always mix with audio only.
That means that all midi has to be converted to audio before that happens.

noynekker
Down the road a few years, when your system and plugins have changed, the midi based soft synths may not load up the same as they used to. If you have frozen tracks, or bounced to tracks, at least you still have the audio rendition in place to carry on.

 
I think this is a major benefit of freezing/bouncing to audio - many times I've gone back to old semi-abandoned projects and not been able to play them back because of changes to my plug-ins. 

Bigdogs

noynekker
Down the road a few years, when your system and plugins have changed, the midi based soft synths may not load up the same as they used to. If you have frozen tracks, or bounced to tracks, at least you still have the audio rendition in place to carry on.

 
I think this is a major benefit of freezing/bouncing to audio - many times I've gone back to old semi-abandoned projects and not been able to play them back because of changes to my plug-ins. 

I agree, and I must get into the habit of doing this...
 
On my old system, using Sonar 6 PE, I had to freeze stuff because my DAW would grind to a halt. Now that my DAW can handle well over twenty VSTi instances, I tend not to "freeze" them. But I know from recent experience, when opening old projects with synths like Absynth 3 (now 5) and Battery 2 (now 3) I've not been able to get those older synths to work, and it's only the fact that I've frozen them in the past that I've been able to pick up an old project.
 
So, yeah... Note to self: Freeze VSTi tracks once the project is finished (my projects are never finished  )

"A work of art is never finished - only abandoned"
 
Leonardo Da Vinci

Personally I work exclusively with midi then i don't have to hear how bad it is..
 
 
But, seriously, there is no hard answer, i think provided that at some point before you end the project that you bounce so that you have a copy of every audio track and every midi track as an archive.. lately i have also been considering exporting the project as OMF as a "portable archive"

I convert MIDI to audio when I want to fade a clip versus fade the track.  I can't fade a MIDI clip.  I don't like enveloping the track, because that means that I can't use the fader to raise or lower the gain on a track, I have to do it in the envelope or insert a bus that I route the track to.  That for me is too convoluted.
 
t
 

I too convert all tracks to audio and hide/archive the midi. Many times over the years this has saved me chasing previously used plugins that I no longer have. Mixing in audio somehow feels like I have more control, though this is based on no measurable outcomes and is almost certainly confabulation on my part:) 

I've never converted midi to audio. And even with older sad computers this was never a problem. But them I use only a couple of soft synths per project. Most of my tracks are audio. 
But all EQ and effects can be added to the track folder of any synth which is really an audio track. 
 
I keep midi open so I can continue to edit if need be. 
I save all projects as MIDI files too for future proofing. I guess I think the oposite as a midi file is future proof, not a CWP file. There will always be better synths to use in the future so why worry about not having a certain sound? And I always finnish songs and move on. My backing tracks are the only projects that I will return to in the future to change and improve with better drums ect.