The key for INVESTING like Todd is doing -- is keeping the properties CLASS A... and investing in great neighborhoods where good people want to live. All the properties I've ever invested in were always class A apartments. You get a better tenant... higher rental rates... and less vacancy etc.
Todd -- I think your rentals should be unaffected by "down the road" events. You've positioned your self well. Great underlying price paid. Low fixed rate mortgage. You'll get good rents because the properties and management are nice. If anything - my guess is you'll be able to RAISE rates as housing prices firm because the prices paid for new purchases will have to be reflected in the rental rates. A rising tide floats all boats. The tighter the market gets with inventory absorption - regardless of who is buying the better it will be for everyone.
We just raised our rental rates 50% in one building I own (an LLC with other investors) and 35% in the one I just invested in (we're doing a major redo of units as they become vacant - raising the quality a long way). Over the next 10 to 15 years these units are going to make nothing but money.
Selling a depreciating asset to buy/invest in an appreciating asset with cash flow is the smartest move you'll have ever made in your entire life (other than marry Kelli). I'm proud of you for having the guts to make the move. 