For loop does not do all iterations

I am trying to create about 500 users in a for loop using wp_insert_user(), but the for loop doesn’t loop fully. It sometimes stops after 20 iterations, sometimes after 50 items, but never iterates fully.

This issue seems to be a general issue with for loop & for each loop in wordpress and not about creating users alone as I faced this issue when looping through users fetched via WP_User_Query.

I have increased the maximum execution time to 60 minutes via set_time_limit(60*60), but still no luck.

Please let me know how to get for & for each loops to loop through all iterations.

I have enabled debug logs and I did not see any errors indicating why it stopped iterating abruptly through the for loop.

// Child theme functions.php
function some_function() {
	...
	wp_schedule_single_event( time() + 10, 'my_hook_create_test_users', $method_args);
	...
}

add_action( 'my_hook_create_test_users', 'my_create_test_users', 10, 1 );

function my_create_test_users($method_args) {
	$default_max_time_limit = ini_get( 'max_execution_time' );
    $time_limit_changed = set_time_limit(60*60);	
    try {
        for($index = 0; $index < 500; $index++) {
            $userdata = array(
                'ID' 			=> 0,
                'user_pass'		=> 'kadjkashdjkad',
                'user_login' 	=> 'my_test_user_'.$index,
                'user_email'	=> 'my_test_user_'.$index.'@email.com',
                'first_name' 	=> 'my_test_user_'.$index.'_FN',
                'last_name' 	=> 'my_test_user_'.$index.'_LN',
                'role' 			=> 'subscriber',
                'meta_input' => array(
                    'my_is_test_user' => 'true',
                    'my_user_type' => 'paid',
                    'my_membership_purchase_date' => time(),
                )                
            );

            $userid = wp_insert_user( $userdata );
            if ( !is_wp_error( $userid ) ) { // check if insert was successful
                error_log("Test user ".$user->user_email." created.");
            } else {
                /* Error Handling */
                error_log("Exception while creating test user with email: ".$userdata['email']);
            }        
        }
	} catch(Exception $e) {
		error_log("Exception while processing my_create_test_users: ".$e->getMessage());
	} finally {
        set_time_limit($default_max_time_limit);
    }    
}