Buying ringtones
Should I buy ringtones everytime I want install them on a different device?
Ringtones are a one-time only download from the store, so if you want to download them from the store on a new device you will have to pay to do so. But you don't have to do it that way, when you buy a ringtone you can connect the device to your computer's iTunes and do File > Devices > Transfer Purchases to copy it over to the Tones section of the computer's iTunes library, you can then sync it to other devices and add it to your backup of your purchases / computer.