I appreciate the replies, but I just can't figure it out.
In the hitchhiker's guide to the galaxy, the answer to "life, the universe and everything", according to Deep Thought, was 42.
On that basis, I will assume the answer to your hop point equation is, give or take, 42 minutes.
Tell lambert_w to go home

Argh!
OK, a worked example. Slush might hate me for doing this, but:
D = 2621404453.0646
hashrate = 769984.646
assume c=200 (although it might have changed - you'll have to find out for yourself).
Then hop point = 0.0164293+1.14254/(1.8747*2621404453.0646/(769984.646*200)+exp(1))
= 0.04942183
Shares mined before 0.04942183*D = 86486769 d1 shares are submitted will, on average,
be worth more than expected. Shares mined after this point will be worth less than expected.
I should reiterate the above is only valid if c is still 200. Since c influences variance to a great extent, it will be decreased when Slushes proportion of the network increases, and be increased when Slushes proportion of the network decreases. Since the Slush's proportion has decreased significantly since it was changed to 200, c may be back to 300 by now.
Edit: That's more like 8 minutes rather than 42 minutes.