That depends on the country. You lose Dutch citizenship if you have dual citizenship and don't live in The Netherlands or renew your passport in 10 years.

.. but it does go away if you don't maintain a presence of some variety in the given countries.

No it doesn't. You may lose right of abode but you are unlikely to lose your citizenship.

Simply not true, at least in my case. I haven't been back to my country-of-birth in over 30 years, and have citizenship in the country of my childrens' birth. When the time came to renew my passport, I was informed that my citizenship in my birth country was dependent on whether I had any connection there any more, and since my birth-country has policies regarding dual-citizens needing to justify their citizenship, this was under question. I needed to either go back and live there for a while, or simply give up my citizenship.

Maybe its different in your birth-country and with your citizenship, but its not true that its automatically given and never revoked in every country in the world. Its a case-by-case basis, depending on the policies of the nations involved.

Actually, he is right about the Netherlands. https://ind.nl/en/dutch-citizenship/Pages/Loss-and-the-revok...