Slow processing K7

Hello
I recently went on a aurora viewing/photographing holiday. I was using a K7, Sigma 10-20 at f4, iso 800-1600 and exposures ranging from 15 - 90secs,cat 6 card and freshly charged batteries.
While my results were encouraging I found that my camera took about the same time as the exposure to process the results and produce an image on the screen. I was using DNG but there was no change using jpegs and the file sizes were about the same as daylight images which appear quickly.
This performance was in marked contrast to the surrounding Nik/Can users and caused a few missed images. Although the temp was about -2 and there was some wind it was not extremely cold.
I wonder if anyone can explain this to me.

Dark frame subtraction/long exposure noise reduction

And over 30 second exposures it can't be turned off.

This should work to turn the DFS off.
https://www.pentaxuser.com/forum/topic/turn-off-dfs-with-your-k20d-and-k7-22673

Not on exposures greater than 30 seconds Stefan

Latest K7 firmware allows you to turn NR off/on but the system overrides these settings on longer exposures (>30secs)

Thanks very much for your help - I'll try switching off the NR next time. I did wonder about black frame but didn't think it would extend the processing time for so long. I presume that the other camera users around me didn't have this system or it was turned off.
Thanks again.

Stefan's link relates to a hack which does (potentially) allow DFS to be completely disabled.

I tried the hack Pentaxophile and the camera still overides the menu settings (NR off)

Here my last correspondence from pentax on the subject

JR reckons that sensor management issues = heat

Well the hack doesn't work then! 'Heat' isn't the culprit as a DFS will not reduce heat any! It will reduce NOISE caused by the heat though. It just would have been nice to have the option to turn it off and do a manual dark frame at the end of a shoot.

Then the only way is to take short exposure and exposure stack them.