Yay! This has to feel like a major factor, or else the Huns' kit won't do much
Ehhh... You might think so, but short wars are very popular, especially if you win. Take the Franco-Prussian war for example. Prussia beat France quickly and handilly, and it was such a popular war that the German people signed on to a German unification shortly afterwards. Yes, France was steaming mad about it, especially with the loss of Alsace-Lorraine, but they ended up just getting throttled by Germany again in the next war. The Gulf War is another great example. Bush Sr. promised to kick Iraq out of Kuwait, and that's exactly what they did. Contrast that with the lengthy and ongoing occupation of Afghanistan and how unpopular and politically costly that war has been for Bush Jr. and Obama.
It's far more important to make sure your own people like you and your wars than it is to keep losers happy. The French and Afghanis were going to hate Germans and Americans, respectively, whether the war took 1 year or 10, but they can blame their own government and troops for losing just as well as they can blame the winners. IRL, the most important thing about wars is that you keep your own people happy by a) winning and b) win as cheaply as possible, and a shorter war is generally a cheaper war.