I refresh the grease in my shackles and spray lubricant (with lanolin) among the leaves. After a dirty run (mud/dust/sand) I pressure-wash the leaf pack and reapply the lubricant.
There are supposed to be wafers in the pack to help it move about, but debris will often get in and cause creaks and squeaks. Hose down the main stuff, pressure-wash the gunk out of the springs and re-lubricate and they work well without noise. Have had mine in for 2 years now and they're still quiet, still performing well with or without the caravan on it.
And last weighbridge I hit with a tub full (really full) of stuff we were 3040Kg - about 60Kg over the GVM, and she still rode well. Thankfully I won't have to be that full again!