What is the life expectancy of a Rustys 2" add a leaf kit? I've already purchased the 2" coils and a 2" main leaf, so I'm commited to the lift. I was just wondering if I should think about throwing an extra secondary leaf in the pack to keep it from sagging quickly. Currently, my springs sit flat, and I don't do a whole lot of wheeling (mainly just sandy, water pits). I also don't carry much in the cargo area other than car parts, groceries and/or a stroller.