If you are not mining LTC at the time a block has been found on multipool.in, but you still have hundreds of thousands of LTC round shares when an LTC block is found, I would have thought you would receive a payout for some of those round shares. These seems not to be the case. I watched the last two LTC block be found according to the Last 30 Blocks Found - LTC table but received nothing for my round shares which are of course going down all the time. This doesn't seem fair as the pool switching is not up to me.
It's PPLNS. Pay Per Last Number of Shares. This means that, say it is based on 10k shares, 10,001 will remove share 1, 10,002 removes share 2, etc.
It evens out to be the same reward over time. You could have hopped on near the end, gotten 50 shares at the last minute, now you only mined for a minute and got a big reward.