I'm here 11 years later, and I had a similar issue. I found out in my instance that it was the audio in my neststed sequences causing the problem. I moved the audio outside of nests and it works normally now (just kind of sucks for keeping things organized).

Still an issue 11 years later. Project is 48khz, all audio files are 48khz, and it takes 90 minutes to render an audio preview for a 30 min sequence. if I want to see the waveforms in the timeline.

Yet I can drop any audio file in after effects, press LL, and it magically shows a waveform without any rendering.

Adobe really needs to stop pretending this is a user issue and fix their program. 

I had the same issue. I had a 90 minute, multicam sequence that was taking over an hour just to render the audio, and it would crash before even finsihing.  Here is what worked for me: I created a completely new sequence, using parameters copied from one that I knew to be trouble free. 

I copied my timeline from my old sequence, and pasted into the new one (btw, this is a good thing to try to solve many problems).

Since I still needed the multicam video, as I am in the rough cut stage, I locked the video tracks, and then flattened the audio tracks.

I selected my entire timeline, then I right-clicked on the audio to Flatten it.  Note: I had to first click "Enable", then right-click again and "Flatten".

I then export. The audio render time went down to about 5 minutes.

Just to be clear, this is not a "Solution", this is a correct understanding of THE PROBLEM. it 2020, can someone please FIX THIS PROBLEM?

I'm not sure if this has been posted, but I had the same problem & super simple solution is:

Create a new seqeunce with any defaul settings, then drop a piece of footage you're working with into the timeline & (here is the key) follow PP's prompt to change sequence settings to match footage properties (this is not the defailt selection).  Once you do this, it will export perfectly with no audio hell render times.  

I have found that the issue is directly linked to the sequence containing more footage than is being exported.  Although there are still mixed bitrates and frame rates the issue is totally resolved 100% of the time by simply creating a new sequence for the footage to export.  I went from 58 minutes of audio render time to 8 seconds simply by copying the export to a new sequence where there was no other footage.

This works.

Here's the real answer.  You do not need to convert your audio files.  Simply go to premiere settings, media cache.  Clear the cache.  You will not loose anything you're working on.

Now you'll be able to export quickly.

Clear the media cache from time to time, you'll be glad you did.

Work-around/solution is quite simple. Make sure the bitrate is the same on your audio, for instance 24 bit. In your audio render settings, make sure you export with 24bit audio. Uncompressed. Then no audio render whatsoever. Straight to encoding video.

I´m having the same problem! And to bring it to the top;

I´m rendering 2sec of Footage!

Here´s a screenshot to proof whats going on here;

Btw;

8* Xeon E5 3,6

32GB RAM

Quadro K4000

Thats really not acceptable!

I'm having this same issue... except.. maybe more extreme than most.  I'm simply using AE to turn my audio files Audio files with a wave spectrum.   my 5 minute audio clips take 17 minutes to render, but never complete because CS6 uses all of my disk space.  my 5 minute audio clip continually uses 50 GIGS.   yes you read that correctly.    Not sure how this is even possible.    But it continually uses it all, I have tried three times.  and its seeming like a complete waste of time. Thoughts?