No it isnt. If you move to another country thats where you make your life. Become a citizen, learn the language, become a part of your local community and contribute to it. All too often Brits go to France for dirt cheap housing, dirt cheap booze, dont learn the language or become part of the community, sit watching UK Sky or Freesat and socialising only with other Brits. I have met plenty of examples, they rush back to the UK when they run out of money or become ill. They have a choice and presently their views or votes dont count. I believe that if they want the protection of the British passport and the use of our Health Service they should continue paying some appropriate UK taxes. Why should they leech off UK taxpayers?
The vast majority of ex-pats are not leeching off UK taxpayers, but paying tax in their country of residence. They are working age And many of them intend to return, which is why they wish to have a say in Brexit. Furthermore, they do not use the NHS, but use local health services, or those paid for by the companies for which they work.
It is estimated that of the 1.2m British expats living within the EU, around 800,000 are workers or those dependent on workers in the family. https://www.expatriates.co.uk/
There are over 13000 British living in Norway, and while I don't have detailed demographics, I know that most of them work here; many in the oil & gas industry. All of the many British I have met here are either working age, or the children of a British person who works here. None are retired. None are milking any systems or leeching off taxpayers. Most are paying more taxes than they would in the UK. The exceptions among those that I know are on generous expat contracts, and still pay taxes in the UK, because they are still on UK salaries.
What you suggest in your post is that BP employees working in Norway should become Norwegian citizens, although I don't think that is what you intended.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom