If you see a fare you can live with, by all means grab it. And, I've been the first person to say that fares aren't going anywhere but up, at least in the near term. But, miracles do sometimes happen.
For example, I've been watching prices for a roundtrip DTW-ORF in late August (beach vacation.) NWA direct on days/times we could live with were $225, then $235, then $245, then $260, but with plenty of K-class buckets still available--the tickets weren't selling, but the bottom-end fare kept creeping up. Over the weekend, I decided to bite the bullet and grab tickets at $225, for connecting flights on AirTran between FNT-PHF (not optimal, but close enough), but hadn't gotten around to it, 'cause I needed to check times and airport choices with my wife.
Lo and behold, I get an Orbitz fare notification this evening that my stop-limit price of $230 for the original flight had been beaten. However, it hadn't been beaten; it had been crushed. Direct flights NWA, ideal time down, the next day back, for $175 pp. Praise the lord and pass the credit card!
Grabbed four of the last six K-class seats, too!