Well there's a few. It's more so a discount on the styrafoam you don't have to pay for. I think it's standard. Shipping is usually 10$
So you'd by a year supply if rats for 60-70$ (if he's a HE you can stop at smalls) You also could look for local rat breeders (some deliver, my guy delivers me my FT every month. And will deliver live every Thursday if needed) just throw some gas $$ there way.
And as far as life span. I believe anything with hair can last 12-15 months and be Eh Ok