Happy New Year, again!

When is saying Happy New Year to someone not socially appropriate anymore?

Today is January 5. Do we need to keep wishing everyone a happy new year?

What if I don't see someone for a couple of weeks, is it still okay to wish them happy new year in February? How about if I don't see them until August?

And why are we still talking about Christmas. It was a week and 5 days ago. Almost 2 weeks later! I don't really want to hear, "How was your Christmas?" Can I ask someone that in June? And then July to Decemeber I will ask them, "Are you ready for Christmas?"