How does c# Lifetime work?

LifeTimeTest.cs

using System.Diagnostics;
using System.Threading;

namespace LifeTimeTest;

public class LifeTimeTest
{
    public LifeTimeTest()
    {
        //TestLifeTime(42);     // Outputs 43 one time
        //TestLifeTime2(42);    // Outputs every second: 43, 44, 45, 46, ... 
        //TestLifeTime3(42);    // Outputs 43 every second
        TestLifeTime4(42);      // Outputs every second: 43, 44, 45, 46, ... Safe to use????
    }

    Timer? field1;
    Timer? field2;

    void TestLifeTime(int i)
    {
        var local1 = new Timer(_ => i += 1, null, 0, 1000);
        var local2 = new Timer(_ => Debug.WriteLine(i), null, 0, 1000);
    }

    void TestLifeTime2(int i)
    {
        field1 = new Timer(_ => i += 1, null, 0, 1000);
        field2 = new Timer(_ => Debug.WriteLine(i), null, 0, 1000);
    }

    void TestLifeTime3(int i)
    {
        var local1 = new Timer(_ => i += 1, null, 0, 1000);
        field2 = new Timer(_ => Debug.WriteLine(i), null, 0, 1000);
    }

    void TestLifeTime4(int i)
    {
        var local1 = new Timer(_ => i += 1, null, 0, 1000);
        field2 = new Timer(_ => Debug.WriteLine($"{local1} {i}"), null, 0, 1000);
    }
}