No time is 'painfully long' if you get fun from it. Yeah, I'm a grinding nerd. ;) Years of playing WoW does that and worse to some people out there :)
The 'Zero-casualties' strategy is another such mind-numbing things: fun for some, awful boredom for most :)

No losses strategy is especially painful if you use skeleton archer without timeback. Losing a couple of those will prompt you to load a quicksave. /shrug

I do not care of loses as long I can win, I have brainless, power strategy using vamps, 80% of my battles end in 3 turns...still the game can take me at least 25 hours of mine time... I just can't imagine how long can no-loss master player spend on one KB game... 250 hours?

I'm a new player to the game and I don't know what the zero-casualties strategy is, but if it concerns reloading if even one troop dies in battle mode, I would agree it would be extremely boring :).

Usually, it involves deep knowledge of every unit/spell/skill/artifact/whatnot in the game and playing with not one single unit killed. Obviously, the units WILL get killed, but then the player applies Inquisitor's ressurection spell/ability, or/and Resurrsction spell, or/and Sacrifice spell. Nobody does that on his first game pass. But, once you beat the game on impossible over and over, this variation of IronMan can squeeze some more juice from the game :)

There are many ways to approach the game. Currently I am trying a no-recruitment game which means you can only play with those units you pick up along the road including items (it can be even more challenging if you don't use any items). The only way to replenish them is by Sacrifice or Diplomacy.