Other than the award level (price), other considerations are:
How firm is your schedule. refunding charge is $150 for members under PLAT level.
In 2015, one-way award is allowed, which provides more flexibility in how you get to/from your destination. For example, if you are trying to get from NY to Vegas, and can only find low-award going to Vegas, you have the option of buying your return ticket with cash (with Delta or another airline!).
Another consideration on how early/late you buy/redeem your ticket is how popular the flight is, especially during your desired travel dates. E.g. - are you flying out the the friday of a holiday long weekend? Christmas? Thanksgiving? If demand is expected to be high for your desired dates, then book it sooner rather than later.
Demand/supply is also affected by where you are flying from/to. If you are flying from NYC to LAX, then there are literally dozens of direct and 1-stop flights that can get you there, so maybe it is worth waiting for a desirable flight time/connection.
Last edited by chunky649; Aug 29, 2014 at 10:42 am