I'll take a stab at it with my thoughts since nobody has responded in regards to release engineering ...
I'll cut the Porteus devs some slack (heh), since current in even Slackware does not mean stability (yes better than most). So if Porteus released on a rigid timescale from the current tree, they may have to deal with endless point-releases if major issues crop up depending on what PV does in the meantime.
Much of it may have to do with manpower. Frankly, since most free-software projects die on the vine after about 5 years, (dev turnover, boredom, ageing, real life etc) I'm quite thankful that they are still around and still releasing at all. I can wait for awhile.
What can we do in the meantime? Depending on skill level, we can replace kernels, compile and swap out busybox, build or update txz/xzm modules etc. Somewhat answering the question of "what if Porteus got hit by a bus?" type of thing.....
I think if we wanted more timely releases, then perhaps we shall all start donating, and donate often, to support a full-time team.

That's a UNIX book - cool. -Garth