Wikipedia defines addiction as "a brain disorder characterized by compulsive engagement in rewarding stimuli, despite adverse consequences"

I think it's important to realize that addiction is not just doing something often (e.g. we all drink water often, that's not addicition). It has to have a detrimental consequence in your life for to be addiction.

Is your checking of HN causing you some problems?

For me, I think, we all need to have a break every now and again, whether it's listening to music, going for a walk in the park, getting a coffee, whatever. I think looking at HN during your breaks is an entirely unproblematic way to spend your breaks.

So unless you are having some problems in your life due to checking HN, you are not addicted to HN, even if you check it often.