I'm not a real big advocate of check valves as a fail-safe mechanism.
In my experience, check valves can place enough back pressure on the pump to cause a noticeable loss of flow. Further, I think it is a question of "when" not "if" it will fail. All our plumbing, the pipes get coated with a slime over time, that will eventually cause the seal to fail in a check valve.
Thus the only way to keep check valves is to routinely clean them out. Thus it's another maintenance chore to keep on top of, and further since it tends to be an "invisible" task (you don't "see" that the check valve is dirty unless you look inside), human nature being what it is, I think the risk is that it will tend to be ignored at some point or other.
Depending on how you have your plumbing, there are ways around having to need a check valve to prevent overflowing your sump.
The first method is size your sump to accomodate all the extra water that drains into it in a power fail scenario.
Along those lines, also make sure your returns are near the surface of the display tank(s) so that the tank(s) don't empty beyond a couple inches off the top in a power fail scenario. Sounds like common sense, but you'd be surprised how many people put sump returns down near the bottom of the tank.
(In that situation, you're
completely reliant on the check valve, and it "must not fail." But there's no way to guarantee this: by cleaning the best you are doing is "hedging your bets." How comfortable are you with risk?)
The last idea I want to share is that if you have your sump return lines come "up and over" the tank wall, if you drill a few holes in the pipe near the surface, these will serve as siphon breaks. As soon as they suck air in a power failure, the siphon is broken. This idea isn't foolproof, nothing really is, but at least you can spot at-a-glance if the holes are clogged and clean them out with a minimum of fuss.
Just my $0.02. HTH.