Uz,
I would dive into some of the larger, broader Porsche-centric forums (rennlist, planet 9, 6speedonline) to get some info about PDK longevity. It's been around since the 2009 model year, so there's going to be limited info on longevity.
That said, from everything I've read, the PDK is generally regarded as the best and most reliable DCT-type transmission made at any price point.
Also: LC wouldn't be on the car if it weren't meant to be used regularly. However, Porsche has specific recommendations about when and how often an owner should use it in the Owner's Manual and the Porsche Good to Know app. Rather than rely on us, I'd read what Porsche has to say about LC first.