Making Purchases for miles
 

OK, so I can make purchases through the FF sites for each airline to extend my expiration dates, is this correct? Has anyone had any problem getting credit for their purchase through NWA, Delta, or UA sites? Do I just need to click on the stores site and it will automatically credit miles to my respective accounts? I do not want to go through a bunch of hoops to get them to credit a few miles, but I do want to extend mile expiration date.

Thanks Again!