My experience with my Roush 427SRTW is as follows:
At delivery, intake gasket was leaking. Roush paid the labor to replace it but I was charged for the gasket. I guess their warranty doesn't extend to gaskets.
At 13,000 miles,
oil use (one quart every 250 miles) and blow-by warranted a complete rebuild. Heads were leaking
oil at seals and guides. Valve stems were worn. Needed complete head rebuild. Rings were shot, needed new pistons, rings, bearings, cam, lifters.
After rebuild, and updated Roush cam and lifters, the engine ran stronger than ever.
So, based on my experience, if you don't drive more than a few miles per year, you'll probably be ok. However, if you plan to put thousands of miles on your car, you might want to consider a custom, hand built engine by another builder (Brent Lykins and Keith Craft come to mind). Costs will be similar but you will get a custom engine built just for you rather than a crate engine sitting in a warehouse and built by an unknown mechanic.
Just my opinion. Your experience may vary.