I believe there are diminishing returns on greater and greater levels of consumption.

If that's true then it would slightly diminish the advantages of making cash offers because a good lender would only need a few more days to process a loan.  

I have been told it does not decompose on it's own and the concentration is not diminished by air exchanges.

If I'd never managed on my own, I would have never learned those things and my profits would be diminished because of that.

Even if you self manage at some point you might not want to and if you didn't allocate for that cost on purchase you will have diminished returns.Most investors can't handle by themselves doing everything anything over a 20 unit property.

With a Self Directed 401k I may have to put up to 50% down to leverage, which greatly diminishes returns. 2.

In addition, your ability to attract a decent quality tenant will be significantly diminished versus a SFR in a good neighborhood.When going from SFR to MF, there is a tradeoff you're making. 

I don't know you, but it seems your heart is more geared towards helping others and if so the daily grind of rental property can diminish your charitable intentions.

Plus with the condo association taking care of most anything that goes wrong your management fee and time dealing with issues at the rental property are very much diminished.

I can't say she is wrong but I can say that her and I are both guilty of the Law of Diminishing Intent.