I always find the sweet spot is 5weeks to 21days prior. Much earlier than that and the high-discount seats aren't setup yet. When prices are staying above the historical price, I've also gambled and bought with less than 10days to go - can get a last-minute discount. But that's really playing chicken with them - and can end up higher. It's only worked about a third of the time for me. OK if by yourself, but not for a family.
I use a site like SideStep because it tracks the daily price on a chart. You can see how the price has fluctuated in the past to better guage if is likely to come down, and when.
Plus you know what the lowest price is, and how much more you would be paying. Even though tracking on those sites, I go to the airline site to buy - to avoid any booking fees.
You'll definitely be paying more for a direct flight, though - and on Delta instead of a discount carrier. It's what is important to you - convenience and travel time versus price.
One tip. If you're buying tickets for a family, buy the tickets one at a time.
If there are only a couple of discount seats available, you don't get them if you are searching for more than that number of tickets.
Reason is they sell you tickets that all have the same price - and if you need say 5, but there are only 3 discount seats left - they sell you other higher-priced ones.
By buying them one at a time, you would get the 3 discount seats, then 1 a little higher, and so on. You can still choose your seats together, once all done.
