This might be wrong(most probably is
) But I have had no real trouble with the tube life in a combo or a head,the combo lasted as long as any head has!!
I owned a Nomad 100 short base combo 1x12" and it was super but I suppose I prefer a head and cabinet is just for me,I run a dual rec into a 1x12" Theile cab and it sounds awsome and looks erm.....a little uneven but hey it sound great
I prefer this combination because I love Noogies,the best tone on the planet but you get that at a cost.....they are heavy fuckers!!! so when I ve finished the gig and Im exhausted I really dont want to carry a combo out to the car I just take my time and take two journeys with the head and combo
Another plus side is that you can keep your cab for the rest of your life and only have the need to buy different heads
I say get a short head for your cab,
Ohh Im also on the look out for a short head to fit nicely onto my Theile but I have time still and the recto sounds ace anyways !!
But yeah I havent experianced the short tube life scenario,
I cant see that this could be a problem because a combo is just a head(the amp) and a cabinet (the speaker) in one box!!!!
Perhaps some of you tech guys here could shine some light on this