Customer's shipping address remains after an order is submitted

The customer's choices for billing and shipping address are saved to their record after an order is completed.  What are the benefits to doing that?

I'm thinking about nulling them when the order is submitted because I don't want to show a Tax amount until they've selected an address.  If they pick a different one than last time then the tax amount will change somewhat unexpectedly.

What else will I affect if the customer always has NULL for billing and shipping except near the end of checkout?

Right. They're saved to apply correct tax. Most store owners want nopCommerce to work this way (there were a lot of forum requests). If you want to null them, then place required logic into ResetCheckoutData method of CustomerService (just a couple of lines)

Thanks, I just wanted to make sure I wouldn't be throwing something else away in the process.  Our customers will most likely ship to multiple addresses so it is important to us that we not show a tax amount unless it's correct.