I'm sorry, did I eat one of your kittens? Because you're being awfully hostile...
What? I'm saying using a stupid plot device to justify stupid stories is a bad thing.
The Catalyst (and by extension, the Reapers) are stupid, poorly programmed machines that take wildly extreme measures to solve problems that have poorly-phrased parameters. "Stupid stories because the Catalyst is stupid" is pretty much the definition of the Shepard trilogy. But just because they are stupid doesn't mean they can't be part of an interesting story.
The Reapers constantly trying to defeat a force that they've already lost to would run completely counter to the Reaper's programming if they kept losing Reapers. The Reapers themselves are the "preservation" of life so every Reaper lost is a failure. Failing to "preserve" life in a blind attempt to "preserve" other life is even stupider than the Catalyst in ME3.
And their preparations were thwarted over and over by Shepard. Until they went "screw it" and entered batarian space with guns blazing.
You're not countering my point. The Reapers were preparing to harvest our cycle since before Shepard was even alive.
When you said suggested they didn't try again.
Did the Japanese continue WWII after America dealt them a crippling blow? No, because it would be folly and run counter to their goals. Continuing to fight a superior force at the cost of your mission is as stupid as it gets.