What is the desired date for your outbound, out of interest?

Remember that you can mix and match airlines too - at the very least, I would have thought you could get across the Atlantic on a decent airline before changing to MS at either Europe or (even better) CAI.

As for "how often is too often?", my experience is that although once a day is usually the most sensible, I end up spending almost all free time I have on the ANA tool and Expertflyer when I'm about to book/change flights. I can't help it...