The coating will obviously degrade over time and 5 years is the manufacturer's suggested life. I'm assuming you should have a warranty card if a pro did it. Realistically, your paint will be swirled in five years and will need to be corrected again if it bothers you. Otherwise, just go about your life and apply whatever protection choice.
There isn't a definitive means to tell if the coating is still present beyond the water behavior. Ceramic can get 'clogged' and in a relatively short amount of time depending on conditions. Typically a good wash with proper soap and an annual iron-x will properly cleanse the paint to rejuvenate the ceramic if you notice the water behavior starting to fade. I do a more serious 'topper' every six months after a iron removal treatment for my sanity. I'm going on year 2 of 5 w/ my feynlab ceramic.