Thank you for your questions. If you were breathing well for the first 6-8 months, and then you began to have intermittent breathing problems, you may have an inhalational allergy or the beginning of nasal obstruction from the surgery. Generally, mechanical problems don't come and go, but persist day and night. Consider taking an antihistamine such as zyrtec before bedtime for a week and see if this makes a difference. If not, visit your surgeon and have him look at your nose for the signs of a nasal collapse.
While there is still some residual swelling likely present 8 months following a revision rhinoplasty, it shouldn't be enough swelling to cause nasal obstruction. Often, some of the techniques we use to define and refine a bulbous tip can actually narrow the nasal airway. It likely has nothing to do with your septum. The only way to tell what is going on his with a careful examination. Make an appointment to see your surgeon and he or she should be able to advise you correctly. Good luck.