Prepayment effect does diminish as the amount of prepayment increases.  

This diminished competition allows me to still find good deals on the MLS that meet my profit margins.

Originally posted by @Scott Smith:In my view, one of the pillar is also equity stripping where you diminish the value of the asset by attaching liens/notes on them from another third party or entity.

At some point you will realize diminishing returns, so just do it.

Annuities from companies (usually called "pensions" or "defined benefit" funds) are usually guaranteed, but they have been largely killed off by companies and diminished by governments to push the responsibility onto the individual over the company. 

Let the Tenant pay off the mortgage and keep your cash free to build up an account for the next purchase.Have you heard of the law of diminishing returns?

We have progressed to diminishing the value of in-person business meetings. 

@David Gauger one challenge with a rent estimator like air dna is that their data is often based on bookings/vacancies that occurred months ago, and the market today is COMPLETELY different than it was several months ago.Specifically, there has been recent data showing that the STR market is completely over-saturated with supply, and most indicators show that we're in recession--which means that demand will likely decrease substantially (or is already decreasing)...it sounds like a perfect storm of excess supply and diminishing demand.

Non smoking tenants (smokers often break the rules and sneak a smoke inside) no candles and knowledge of electrical appliances throughout the house hugely diminishes risk. 

Appraisers constantly build their knowledge base through experience, forums, symposiums, field work, and resources like the MAI - the comment about 1970's calculations demonstrates an ignorance of fundamentals - not the least of which is the economic law of diminishing returns.