In my opinion every block actually discourages big players from aiming...while it may hurt to see them abandon at high difficulty, a longer time gives more constancy to hash rate.  I think a middle ground that would be a pain to monitor, but less often than every block (maybe 30-50 or less) would give more incentive to set and forget-maybe change every so often.  While small miners want the difficulty drop, those invested in it wanted it to raise,  finding something in between would give big guys a reason to hand around, at least more often, and little guys more of a chance.  In the end if, you really want a coin to be worth something you want a higher difficulty, if you want to make it as a miner you want a lower difficulty.  Gravity in my opinion encourages a much lower difficulty.  

I might be completely wrong, feel free to argue or correct me.  I'm not trying to say this like I know what I'm talking about, but that's how I see it.