We can only answer this question based on anecdotal evidence from our years of inspecting nearly 8,000 houses and mobile homes, because we found no professional research with specific numbers. Here’s what we know:

•   Increased occupancy reduces the life of replaceable interior components of a home that the people come in contact with, such a carpet, interior paint, cabinets, plumbing fixtures and appliances. Septic drainfield life is also shortened.
•   More people living in a house does not have much effect on life of the structure or roof. Quality of original construction, moisture control, and level of overall maintenance are the key factors.
•   The age of the occupants also affects the life expectancy of replaceable interior components, with young families being hard on an interior and senior citizens generally more gentle—with the exception that seniors with a mobility problem in a wheelchair can be rough on cabinets and walls. 
•   The number of occupants tends to shorten the life of mobile home components more than site-built houses, but they have an inherently shorter life expectancy to begin with.

    Also, see our blog posts What is the average life expectancy of a house? and What is the life expectancy of a mobile home? and What is the average lifespan of the parts of a house? and How accurate are the average life expectancy ratings of home components? Are they actually useful?

       Visit our LIFE EXPECTANCY page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.