When to purchase?
 

I need to purchase two tickets to from DEN to DTW in August. Right now they are about $450-500/each, almost $150 more than competitors (F9, NW). For various reasons, I really want to stay on UA. Should I pull the trigger now or hold out? Any good tools to help 'guess'?

Buy now, refare (over the phone, taking screenshots) later.

farecast.com provides a "fare forecast" tool for many combinations of U.S. cities.

Actually, I'm seeing a lot of $352 fares for DEN-DTW in August. But maybe you need specific days.

I haven't had much luck refaring. I believe that refaring might not help you if (a) you purchased the original ticket using some kind of voucher or coupon or (b) the lower fares are in a different fare class than what you originally purchased.

Tag your flights with Yapta.com. It'll keep track of the fare changes for you automatically, and send you an email anytime the price drops.

Both of these cases can be refared.
(a) You usually have to quote the "guaranteed airfare" rule.
(b) Unless you care about refundability or upgradeability, it doesn't matter.

Yapta works fine if price is all that matters, but for flights where you intentionally purchase a higher fare class for refundability or upgradeability, it's useless.

Depends on your elite status, if you're 2P and up, and the time and route is not extra crowded, I would book 6-2 weeks before the flight time. Since UA's promo sometimes only good for 1 or 2 months, esp those 10% off coupon, which you can't refare with.