I don't think most places sell 1 or 2 day tickets. There's no discount so it's better to get them through Disney. I guess in theory, you can stock up on 1d tickets to avoid price increases. And if on any trip you decide to spend more days at the parks, you can "upgrade" your 1day ticket to more days.
When do you know you'll get the comp tickets? After you've gone into the park? and how many days do you typically go? Currently Cheaptickets with Ebates gives me the lowest cost for 5day tickets. You can buy that, link to your
MDE and book FP. Once you get to Orlando and receive your comp tickets, go through the gate using your comp tickets rather than the 5day tickets.