Consistently taking non-daily medicine: When it’s time to replace it

I have a minor medical condition for which my doctor suggested an over-the-counter nasal spray, Flonase  (fluticasone propionate).  Sometimes, for months at a time I’ll take it daily, sometimes every other day, sometimes less often, which my doctor says is fine.  The bottle says it contains 120 metered sprays.  How to know when it’s time to replace it?

I keep a scrap of paper and a pen next to it in my bathroom, writing down the date as I administer it to myself each time.  I can count the dates I’ve written so I know when to get a new one.  By doing that, I don’t throw away a bottle with usable medicine, nor keep using a sprayer with no medicine.

This could be useful for anyone who wants to consistently take medicine.  It’s most useful for medications you’re taking on something other than a daily basis.  For daily medicine, a seven-day pill box organizer, or something similar, is probably more convenient.