BLM is a bit weird when it comes to parsing because we can go FOREVER.
Unlike other classes which are limited by TP or MP, and can only go all out for 2-3, maybe 4 for DRG, minutes.
But at the same time, we are the most proc dependent, so you could have a LOT of procs in the first minute, and then a lot less for the next 4 minutes.
This is why I always try to do a 5, or even 6 minute parse on my BLM, for 2 complete rounds of Raging and Convert.