Keep Your Original (Secondary) Google Voice Number Forever.

If you originally got an Google number and later on if you;

Changed Google Voice Number,
Ported You Home or Soho Office number to Google Voice,
Made your Sprint Number the Google Number,

Then you will have two Google numbers for 90 days. After the 90 day period, Google took back the original number.
But if you are attached to your original Google Number, Google Voice is allowing you to keep the number now! So your friends and family will still be able to text or call you on the original google number but when you call out or text, your new number will show up as the caller ID.
So if you would like to keep the original number, get to the settings tab, and click "make permanent" next to the number you want to keep. (There is a one time $20 administrative fee)
Go ring those numbers! and if you need further help, Google Voice Help Centercan help you.

Google Voice Blog: Make your secondary Google Voice number permanent