How long should I wait to purchase my airline ticket? If now, will it still be good in May?
You purchase for particular dates of travel, and the ticket is good for those dates. So you can purchase now for dates in May. But as others have said, be sure of your travel dates because it can be expensive to change them. It’s hard to predict fare changes; sometimes it pays to book early for better fares, sometimes it pays to wait.
When purchasing your ticket in advance you want to make sure that your plans are set. The cost of changeing a ticket can be more than the original price. Most airlines allow for you to book about 300 days in prior to travel. The other option is to buy a fully refundable ticket if your plans are not set in stone. Airlines that I noticed have ticket rules that allow for changes without change fees or not over the top are Southwest Frontier Jet Blue and Virgin America. I would avoid US AIrways American and Delta. Prior to purchasing your ticket make sure to read all fare rules if you buy from hotwire as some of the tickets are use as is and no changes are allowed.
I’ve heard of people purchasing tickets 12 months in advance. Once upon a time it was cheaper to buy them further in advance, but not so anymore. The flip side of that is, there is no hurry to buy them either, you technically can buy them on the day of departure (as long as an e-ticket), so no need to rush around. But, as the answers above say, generally once you’ve booked you will not be able to change the dates (or will incur a fee to do so), so be sure of the dates before you book. Otherwise, yeah, shop around, check internet sites, and if you see a good fare then grab it.