"RE: When to get a new system
My main reason for asking, if there is an issue of shedding, has anyone attempted ventilating new hair into the piece? I've looked up tutorials for ventilating hair, and it really doesn't look hard. So I wonder if that could help increase the lifespan of a piece if you gradually added new hair where it is falling out. Just a thought."

That's actually not a bad idea! Adding a few single hairs hear and there, especially at the hairline, to keep things looking good is a great idea. You'd need your own supply of remy hair though. I wonder if TL can supply a small section of remy hair for a reasonable cost for just this kind of thing.