I have bad allergies and am on Rhinocort - but have used Flonase in the past. If I miss a dose, I feel bad, because the medicine isn't there to stop what it's supposed to stop - in this case, inflammation. With Rhinocort and Flonase, at least for me, it can take a few days of the normal use for me to get back to feeling normal.
I use allergy meds all year round, so I don't stop usage based on the season.