Believe it or not, I just upgraded my old Drupal 6 instances serving e.g. my blog [1] to Drupal 6 LTS v6.49.
Thanks a lot to Elliot Christenson for continuing Drupal 6 security support. See [2] for more information about Drupal 6 LTS support provided by his company.
[1] https://sunweavers.net/blog
[2] https://www.mydropwizard.com/blog