One possible idea I can give you would be to add an indicator to suggest when the timing of a donation would provide the best incentive to p2pool miners. If donations are made on the same day p2pool finds 5-6 blocks, the situation could inspire a "quit while the going's good" attitude for someone who's getting anxious to switch to a low variance pool. If an indicator (red-orange-green maybe?) were to discourage donating until "last block found" goes significantly above the "time to block", there could be an improvement in the variance over long periods of time.
Hopefully enough donators might follow a timing indicator that it could really smooth out the variance as it's directly experienced by p2poolers.
Interesting idea, although I worry that donators may not have the patience to keep checking back to see if it's it's been a long time since the last block. It might just stop them donating when lots of blocks have been found, and reduce their overall donations over time. Do you think this will be a problem?
I agree it'd be nice to smooth variance out, but I think that will also work if we attract as many businesses to 1% decentralization as possible, with weekly donations at all random times. Even if payments get grouped up so a period of time seems donation lucky, overall it should mean there is less "super luck" during the week where you get lots of blocks and lots of donations at the same time. It's possible, but the chance should be lower than just looking at p2pool luck, shouldn't it?
I'm very conscious of this and have been trying to figure out what the best default/minimum cutoff should be (0.0001 only goes to about 13 miners with 0.01btc, the typical donation amount, 113 with 0.00001). The bitcoin reference wallet lets you now choose which inputs you want to put, so you can very easily reroute dust payments below the transaction fee (0.0001 per kb) to a new address, or combine dust with larger inputs. Ultimately, you can see it as the donations might save you a fee if you pick the right inputs for a larger payment (1 larger and 4 dust payments - almost no fee on the larger one).