Yep, that sounds right. What's the cutoff? That particular worker ran for many days in the last round, it just wasn't run in the time frame immediately surrounding the solved block due to some air conditioning issues that came up.
I think the current half-life is about 550 shares. So if 5000 shares were submitted after yours your payout will be close to 0.
Think of this as a gentler version of solo mining. You don't have a good chance of being rewarded for blocks found while you were out, but your variance is much lower than solo when you're in (and on average it's the same whatever you do, and all that).