Doesn't this scoring method encourage pool hopping?
I mean, what is to stop someone for creating a tool to mine this pool for only the first 15mins or so of each new round and then jump over to another pool, a PPS perhaps.
Lets say your payout average is .25 a block on Slush and .20/hr on a PPS. Lets also say that out of 20 rounds, Slush has 5 10min blocks and 15 2hr blocks . The hopper spends 4hrs or so on the pool and gets full payment for 5 blocks in addition to a consistent rate from their PPS pool in between.
Over the 30 hours:
The hopper gets 1.25 from Slush, + 5.2 from their PPS. Earning 6.47 BTC.
Loyal slush miners get full payment for 20 blocks. Earning 5 BTC.
If slush had 20 rounds all 2+ hours:
The hopper would get nothing for their 5 hours, and they only spend 5 hours even if some of those rounds are 4+ hours, but the other 35+ hours spent on a PPS they earn at least 7 BTC.
Loyal miners would earn 5 BTC over the 40+ hours.