If you opened the exchange with the intent to hold the property for investment, and then in the future circumstance changed which caused you to reconsider the use of the replacement property and convert it to personal use, then a period of time less than two years might be reasonable.  

If there's enough duplexes that it's likely you find one you like in a reasonable amount of time (less than a year), then start looking at them in your preferred area.

Although the study may increase the gain, the gain may be taxed at a much lower rate making it a beneficial investment.If a property is purchased with the intention to flip or own for a short period of time (less than 3 years), a cost segregation study may not be significant.SHOULD I GET A COST SEGREGATION STUDY BEFORE OR AFTER REHABBING MY PROPERTY?

What caught my eye was how timeless your question is - high prices and tight cash flow are still big challenges here.

As far as break even cash flow on the rentals, it's the timeless question of cash flow versus equity.

@Ava Petruso Oh, the timeless question: to hold or to sell.

Plus you get stays of 90 days or 120 days or whatever at a time. Less

Ayn Rand is timeless !

I know grey is popular but I don't think it's as timeless as the more natural options. 

A vertical fence definitely has a timeless look, and it makes sense to go with something that complements the neighborhood.