Discount shipping over X amount ordered

Hi,

I am not sure which will be better, discounting shipping cost or free shipping in the event of refund requested.
It will be better to have free shipping with conditions if the terms and condition says if you change your mind and you want to return the purchased products, we will refund the amount less the shipping cost?

I am tying to set up nop commerce that a customer will get discount of shipping cost at 50%~ 100% if he purchases products over certain amount.

I set discount as below.
FreeShipping Over X
assigned to shipping
Use percentage
Discount percentage: 100%
start date 1/1/2013
end date : 1/1/2030
require coupon code: (unticked)
dicount limitation: Unlimited.

  in the reqirement,
  discount requirement type:  FreeShipping Over X
  required spent amount: $200.00

I tested it over $200 but it didn't seem to work. is there anyting I was missing?

thanks

"Customer had spent" means had spent in prior completed orders:

https://www.nopcommerce.com/boards/t/20029/applying-discount-to-shopping-cart.aspx

Thanks. your explanation makes it clear.