I'm doing the same thing, it's the only strategy that makes sense to me really.

You could try to find the window where EOS would cost the least. However, then you're actually timing two markets! The EOS market and the Ether market.

Seems to me like the best bet is to determine how much you want to put in this ICO. Then buy one fifth of those Ethers over the next few days and put them in the first window.

After that, I would only participate once a week instead of daily, do to transaction cost and time investment. Cost average the buying of Ether during the week and then put them in the ICO window on Sunday for example.