Yesterday it took me about 14 hours to transcode 320GB of media (h264) to Dnx36. That was on a 2009 iMac Core duo 3.06 with 16gb of ram. Now I'm on a 2012 12-core (2.4 ghz) mac pro with 32gb of ram and I'm rendering out BITC on a 1 hour sequence and need to do that for another 5 hours. I've also transcoded media to an offline res before and frankly it isn't much faster. I'm sure Ram doesn't come into play here much, but I was wondering what would I need to build to get a decent machine to render/export/transcode? I always just edit in offline and don't do any finishing or heavy effects. The only bottlenecks I ever experience are with these issues of data input/output and renders.
Is processor speed more important? I have a suspicion that even my old iMac at home imports and transcodes faster than this much more expensive 12 core, but obviously if I'm doing 8+ files for export in Sorenson, this beast wins and ditto for things in after effects.
Your graphics card may be something to look into as well. I don't know what you're currently using, but some of the new ones have features that can help accelerate the render / export time. Someone else will probably have to speak on this one, however. But I think nVidia would be a good place to start researching.
However, I don't know what your budget is like, but Telestream Vantage might be a good option now or in the future. It offloads the exports to a centralized server. It requires an Avid Transfer manager (I believe), but it can automate your workflows and free up some time on your workstation. You still have to render, but the encoding would be handled by Telestream.