If you're wondering how long the stock springs last, my left pack cracked at around 10 years and 160k miles. This is with average to above average rust and towing over stock capacity (16ft cargo trailer) about 1500 miles with helper springs. I loaded a pallet of roofing shingles with the helper springs, and the bump stops engaged. I tried driving like 2 miles at 25mph then turned around returned that pallet.
If you push your truck, I don't see how it won't be a similar experience to what I had. They'll last at least 150k miles and 10 years. If you are in Florida and never go offroad or carry a payload I'm sure the springs will last 300k mi and 20 years.
FWIW I didn't want to get custom springs, so I went with OE replacement 3/1 leaf packs from Rock Auto. Lift is too high, so I'm going to remove the spacers and install shorter u bolts to get it closer to stock level. If it looks great maybe I'll share a writeup.