Actually, I was thinking about it a bit more this morning, and found another interesting 30 year stretch: from the declaration of war in WWI to the close of WWII in Europe (VE Day) was about a month short of 31 years. Taking it to VP Day is about 1 month into 31 years.

So both world wars and everything that happened in-between took 'only' 30-ish years. :)