While I understand why you are asking, there are a few things to consider.
Some people have addictive personalities. They tend to do what they like to excess, often to their detriment. If it wasn't the vape it would be the cigs in all likelihood.
So yes! Harm reduction.
Is it best to be excessive in anything we eat, drink or breathe?
No! Of course not. Some will abuse or consume too much of almost anything. That is their choice as they will pay the consequences sooner or later.
Many of us, as we age, begin paying for "the sins of our youth"
we understand that we may have been foolish and had we known better we would not have over done it as much. We are more cautious now.
I agree with the poster above that the wildcard is the food grade flavourings. To minimizes the risks I DIY at around 2-4% flavouring and vape as much as I want.
Is someone who vapes juice with 20% flavouring more at risk than me? Seems a logical assumption but we do not know for sure.
Pretty sure though it is still massively less harmful than consuming tobacco, but we each must make that call for ourselves.
Cheers.