Out of all the guys here who own a diesel,I'm probably the one who racks up the least miles--I have had my '82 GMC since 2003,it had 34,000 and change on it then when I got it--yesterday,it just turned 42,618 miles...
Most of my trips are short runs to the dump,plowing my driveway (if its snows much--most years it did,and it got a lot of use and not babied much either)..when I go to get groceries or food its less than a 10 mile round trip,and the few friends I visit only once a week maybe are also about the same distance away..
I cannot recall ever driving it more than 50 miles away from home once one way,in fact..
I had other vehicles available then to use on longer trips..
I have used up a set of glow plugs starting it so often,and the original direct drive starter had acted up after many years of hard cold starts,I figured it was a junk solenoid,it would just "click" and not crank--I swapped in a gear reduction starter I already had,and that one also failed to "kick" when I'd turn the key at first--so the original starter may not be defective..now that the starter has had some use it kicks in every time..probably old wiring to blame..
I have had all gas powered trucks before this pickup and the '85 Burb came along,and my driving habits haven't changed much since 2000,the gas powered trucks could sit just as long with seemingly no ill effects,provided I did drive them at least 100 miles every few months--you could tell when the gas was getting "old",they would not start and run as well and would smell rich,and the engines sounded like they had sticky valves until they fully warmed up..
My diesel Burb has sat since I bought it in 2009 and it had a full tank (40+ gallons) of a combo of diesel and some kerosene,the former owner admitted to using "alternative" fuels like veggy oil and Lord knows what--it always starts and I have let it run a good 7-10 hours over the years every few months--the engine starts a bit hard,but once its running it still sounds as good as the day I got it..
I'd say a diesel "not being good for around town use.they prefer being driven at speed for long distances" may be just a myth,maybe not..all engines suffer to some degree when used for short runs,especially in cold climates,but the diesel doesn't suffer as much in my opinion,being its using oil as fuel,not a "solvent"like gas, that washes lubricants off moving parts..
You'll use up more glow plugs and starters if you only go short distances with a diesel...