7 years or 105,000 miles, whichever comes first. Use HONDA (NGK) plugs.Unless your having problems , it's a waste any sooner.
you may just need to re-gap spark plugs. e3 is my preference for replacement but any premium grade plug will be sufficient. re-gappng plugs is also a good oppertunity to examine coils. if you wait to long to replace or re-gap, you run the risk of plug seizing to the point of breakage. this is why 50,000 miles. use never seize on plug thread on re-install.
Iridium plugs--trying to re-gap can make worse(sorry arturo08).