QUESTION: Kernel and LTS relationship

[newtusmaximus]

  A LTS is supported for 5 years from issue.    After that date the  user  is in freefall if he/she doesn't upgrade to next LTS?  However if user stays with an older LTS but keeps upgrading Kernel, does this extend the life if the original LTS.

The reverse scenario – Take for instance LL3.0 – if user down grades the Kernel to say 3.13 for hardware compatibility reasons, After 2019 ( when the LTS for LL2.8 expires; Kernel 3.13 being the standard for LL 2. 8) does the system  become vulnerable, assuming all updates are maintained??

I.e what is the relationship between Kernel and LTS re longevity/security./vulnerability. ??

Objective to keep older machines working (safely/ non vulnerable) for as long as possible.

PS , not sure where the emoji came from; can't seem to get rid of it.