I've had Sprint since I was 19 and I get loyalty and a grandfathered plan which has unlimited data without being throttled down. I get 10 dollar of the monthly price so the galaxy s9plus is costing me 672.00. I can also trade it back In with galaxy forever program. But the business discount is great.
Grandfathered plans isn't the same as special discounts or offers versus others. It's just letting you keep the plan you got when you joined.
I was mainly talking about the discounts that you get such as free accessories or sometimes even a special offer that other customers don't get because of your time with said carrier.