Hey y'all! First time posting so let me know if there's any forum etiquette I'm lacking on.

So I've got this 2009 XLT with the Superlift kit, and my driveshaft seems to be going after only 8-9k miles with the lift on. I'm getting Superlift's (hella expensive!) double-cardan replacement driveshaft with the hope that it'll stop my car shaking, but I'm wondering: Superlift says the factory driveshaft will last up to 20k miles, but most posts I can find show the driveshaft wearing down well before then. Plus, they don't specify exactly how long their "heavy-duty" replacement driveshaft oughta last. This makes me a bit worried that their $800 replacement part is still gonna become a constant wear item, and I just don't have the wallet for that. So I guess my question is in two parts - first, how long do you think the replacement driveshaft will last? Is it still gonna be a consistent replacement, or do you think it could last the lifetime of the vehicle? Second, if/when the driveshaft does start wearing down, can I just replace the u-joints on it like any other? I know a double-cardan design is essentially two u-joints, but I'm not sure if there's something proprietary about it that'd prevent me from fixing it up.

Thanks for the help in advance! I'm super excited to be here. I love this truck - just hoping that one day he'll stop falling apart on me.