The only issue is you can only take them for a few days straight, or you’ll have rebound congestion when you try to quit. There are oodles of stories online of people who didn’t heed that advice and upped their dosages again and again for months.
Here’s the best method: Afrin (etc.) at night so you can sleep, and during the day if you have something particular important going on. The next day, after you wake do a sinus rinse with xylitol. This clears out the Afrin preventing dependence, but xylitol also keeps things somewhat suppressed.
Continue until cold is done. Source: me, a person with a ridiculously bad immune system that has multiple colds a year that last 3 weeks with nearly full congestion.
(Also, Adderall is great for colds)