A relay will make the contacts on the horn button last a lot longer, especially if you're running a 6V horn on 12 volts. Of course, that depends on your personality- - - -I've used my horn maybe three times in the past 6 months. Saw a bumper sticker a while back- - - - "Horn's broke- - - -watch for finger!"
LOL!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!