Looks like there's a pattern to how these sales unfold. If demand is on Frontier's side then they can fill in gaps like Tue/Wed./Sat. at good-but-not-great levels as an opening bid. Prime times like Sundays and days around certain holidays can still be sky's-the-limit.

Hardest-to-sell days include traditional low periods like late September and the week or two around Halloween. With those it seems you get successive waves of more-generous sales (sometimes offered via DD before offered to everyone) with the grail being the $15 OW anyone can buy (or $15 DD/$19 general public lately). But those don't pop 'til late and come with typically very short-term travel periods (e.g. next 10 days).

So do you take the $49 deal earlier or hold out for the $15? It probably depends on how motivated you are to take the trip and how much flexibility you have...if you have a lot of flexibility you can wait it out.

I did on the Halloween weekend and got ATL-PHL-ATL at $30 RT (not as big a prize as DEN or LAS in Sept., but the schedule worked out with an early outbound and late return).

Generally it pays to be aware of when the very lowest travel periods are and to leave open the time and be ready to pounce.