You will receive your payout immediately in your wallet when a block is found. If your share count has been reset back to 1, then your p2pool instance was probably restarted and you've found a single share since then.

So you are aware share != block, and shares will expire (currently) after 24 hours, soon to be 36 hours, although the share count showing on your p2pool node website does not go down when shares expire, it just keeps counting up how many have been found since the node was restarted last.