I know this person that common courtesy doesn't apply to. If I don't reply to a text or a missed call from them within 5 minutes, it's always quickly followed by another 10-15 texts or calls one after another. When I text them, it could take up to 2 days to a week to reply (usually when they want something).
If they post something on Facebook and nobody comments, they lose their mind. When I share some really good news to them, I get nothing; not even a congratulations, good job or anything.