Begin by understanding RE basics, the tax advantages, financing, market influences, repair estimates and maintenance to apply to your operation, but the 7-12 year range is mainly due to tax depreciation taken beginning to diminish over time, the greatest advantage is in the early years as appreciation is not considered nor increased rents for depreciation. :)

It is also the only way sellers will be able to unload distressed properties that are un-mortgageable.But if you are looking for fairly turn-key properties the advantage of cash diminishes and may not be worth it to you.

Do you recommend staying away from irregular builds altogether since they diminish the effect of luxury improvements?

Your cash flow will decrease from both vacancies and maintenance, which will diminish your return. 

As time passes, the return from the capital paydown diminishes, even more than my curve indicates since 5% appreciation increases the equity, but the rent will go up. 

The down side is increasing taxes reduces economic activity, so it has diminishing returns. 

Stop diminishing your sex and strength 'as a woman'

Again, there is probably a point of diminishing returns on how much board I could get for the stalls vs how much it costs me for the insurance and maintenance on the barn, pastures, etc. 

This concept is very important because the liability protection afforded by a Corporation or LLC can be diminished or even eliminated if the principle of "Alter Ego" is ruled to apply to your entity.

Don't diminish its value being nay-sayers.