I am always scrupulously honest when dealing with insurance companies.
For example, I get a discount on my car insurance as I keep my car garaged overnight. Whenever I am unable to do so, I telephone my insurance and tell them the car will be elsewhere.
All insurance companies are businesses with the sole aim of making a profit. If they can find any reason whatsoever not to pay out, or pay out a reduced sum, they will use it.
I pay my premium because I want to be able to rely on claiming should the need arise. I will not give them an excuse not to pay up.
With smoking, my house insurance went down when I stopped - there is a much reduced risk of fire. :)