They stay with you if you choose. What's kind of sentimental and nice is that the area code stays with you as marker of where you're originally from no matter where you go. It says "this is where I was from as a teenager when I was first allowed a cell phone."
I don't know if this coincided with trend of getting an area code tattoo to signify where you're from, but that also is something that is done by some.
I remember the happy days when a telephone number (also an email) was a ephemeral, changeable thing. Not a permanent unchanging form of ID.
Alas, if you move out of the country for a period of time, it is a challenge to maintain the host country phone service. So there are no guarantees that you can hold on to that signifier of "this is where I was the last time I wanted to get a new phone subscription".
When was that? My parent’s landline number stayed unchanged for 20 years. Through moves, too (with the caveat they stayed in the service area of the CO.)
I don't know if this coincided with trend of getting an area code tattoo to signify where you're from, but that also is something that is done by some.