I just bought an open jaw from Memphis to Milan, Naples to Memphis. We bought 3 months prior to our trip. In my experience, the sooner you buy, the cheaper they will be. My sister, who is accompanying us, got tickets six months ago for 20% less.

Almost a month ago, I bought tix Boston to Naples in October for a hair-raising amount of money, but I wanted to know for sure that we will be going, didn't want to wait for a possible bargain, thought it unlikely that prices would go down, and found flights that had very convenient times. However I signed up for a price alert just for the heck of it, to see if I'd made a big mistake. So far, I got one alert that the price had dropped $30 (a drop in the bucket compared to total price of ticket). For me, it was worth possibly paying more than I might have had to to get the flights I wanted and have that vacation as a certainty that I can look forward to. I might change my mind later, of course.
I used BudgetAir and it was a very smooth process. When I couldn't make seat selection on Alitalia website, I called them (alas, no 800 number and they're in California)they were very helpful and made our seat assignments for us. I keep thinking I should call Alitalia and see if all is in order but haven't done it yet. Never used BudgetAir before but checked around and didn't find anything negative about them on the Web.

In my opinion prices also also varies on what day you buy them, so I would check more than once.

I've been watching a ticket for my Son for the same flights my other kids and I are flying (we got them with miles, not enough for 4)

The roundtrip DEN-BCN 6-9 to 7-2 during the weekend is $1,460 then on Tuesday it drops to $1,240.

I will see how much more its tomorrow to support this theory.