不同國家永久居民(年)

If you want to know each country's immigration law, you can go to the web-site of those country to find out.

Many countries allow you to leave for a period of time. As long as you can prove that the country you want to apply for residency, you can go traveling or working. I fly out of US all the time, they did not count the days I traveled when I applied for my citizenship.