Hi Gene, I'm right in the middle of doing all this with Miles' Live Evil which I just got yesterday.
Using Foobar, Disc 1 took 15:45 (including 5 stereo and 5 multichannel tracks), with PCM Samplerate set to 176K and DSD2PCM Mode set to Multistage (64p). I think I read somewhere that this mode is the most accurate, but also uses the most processing power. Dunno if output sample rate has any effect on processing time.
Also, the above figure doesn't include Replay Gain calculation time, which took an additional 1:23.
The .iso file is 3.7 GB, the 176K FLAC files add up to 6.3 GB. I could probably get by just fine with 88K sample rate, but since my hardware resamples everything to 96K, I guess my thinking is I'd rather have it downsampling instead of up. Of course I have no solid data to back up this theory. ¯\_(ツ)_/¯
I have the same problem with trying to do this during playback; my otherwise-adequate little cheap netbook struggles with it.
[EDIT] Oops! At first I thought my numbers were comparable to yours, but I was misreading; mine seems to go more quickly. This is on a desktop with a quad-core 3.2 GHz processor, so maybe we're just seeing a difference in processor power here. This particular task is pretty number-crunchy, typically maxing out all available processor time - just the sort of thing that tends to reveal the true top speed (or lack of same) of a lot of laptops/netbooks.