When luck is good, then PPLNS system is great to be on. When luck is bad, then PPS is better.
Luck can change at a moments notice.
I personally am not worried about luck. My concern is what if something is broken and we can't find a block? Computers and systems break all the time.
Another thing always bothered me as well. Every time someone else finds a block, we have to restart our search. Perhaps all the restarting is causing an issue?
Again, forgive my ignorance.
I am new here - have been mining on Slush mostly before - but the search restart has always happened and has to happen with every pool. Looking at the historical distribution numbers they look about the same as what you see on a larger mining pool - just that the time between blocks has to be multiplied by a large factor (and the rewards when they do show up have to be multiplied by approximately the same factor). I have seen several blocks on Slush that were proportionally as long as this one, but with their higher hashpower you get through them in 7 hours or so.