surely the damage has already been done...
It's always worth stopping. The body is amazing at healing itself.
The damage has been done, but you can always do more damage if you continue to smoke. It's worth quitting even after decades of smoking.
Surely vaping is a good technique to quit smoking. Recent studies have shown that a person who has adopted vaporizer are able to quit their smoking habit and unlike e-cigarette, it is not containing nicotine and many of the vape formulations like vitamin b12 vape pen contain vitamin or mineral supplements.