Well, listening to it would be a start.
If you want to get a feeler gauge and check, it's not very hard. I haven't done the K24 but I assume it's the same as all other Honda's from what I've seen and read. That is to say it's not a terrible job with a flathead screwdriver and either the valve adjustment tool (basically a deep well socket the screwdriver fits through) or an offset wrench. The magical tool is in the 20 dollar range, I don't have one but I can see where it would save time and frustration (it lets you hold the adjustment screw while you tighten the lock nut).
You're kinda at the mileage where if it's going to happen in the life of the car, it might as well be now. If it sounds tappy, or if you have the time, at least checking the clearances would be good and probably take an hour.