Will an extensionId ever get reused/resassigned to another user?

I'm working on pulling call & message activity into our data warehouse via the RingCentral APIs. I'm currently consuming the following APIs:

- Get Company Call Log Records
- Message Store - Get Message List
- Get Extension List (also necessary in order to get Message Store data, because that API requires iterating over extensions to get all messages company-wide)
- Get Company Directory Entries

I already know that we intend to recycle extension numbers over time as folks come & go from the company. Therefore, I need to account for the fact that for any given extensionId, the extension number could change, thereby affecting my ability to link historical calls to the correct person if I'm not careful. (I'm planning on treating the extensions as a Type 2 slowly-changing dimension table on my end to handle this.)

However, what I don't know is the lifecycle of an extension record itself, based on the extensionId. So, I'm looking for some clarity on that.

Let's assume my own RingCentral extension looks like this in the Get Extension List API:

{
  "id": 123456789,
  "extensionNumber": "420",
  "contact": {
    "firstName": "Chris",
    "lastName": "Harmon",
    "jobTitle": "Data Engineer",
    "department": "Foo Corp",
    "email": "charmon@foocorp.com",
    "emailAsLoginName": true,
    "pronouncedName": {
      "type": "Default",
      "text": "Chris Harmon"
    }
  },
  "name": "Chris Harmon",
  "type": "User",
  "status": "Enabled",
  "permissions": {
    "admin": {
      "enabled": true
    },
    "internationalCalling": {
      "enabled": true
    }
  },
  "hidden": false
}

As mentioned above, I already know that extensionNumber 420 will eventually be recycled & assigned to someone else if I leave the company.

My questions are:

1. If I leave the company, what happens to the RingCentral extension record with extensionId 123456789? Does it remain associated with my user forever, or does it go back into a pool of available extensions to be reassigned to someone else?

2. Is it possible that extensionId 123456789 could be reassigned to a different user (and myself reassigned to a different extensionId) while I'm still at the company?