Google just announced on the Google Voice Blog that if you change your Google Voice number by porting in a phone number from another carrier or use the “Sprint Option 1 intergration,” you now have the option of keeping your initial Google Voice number permanently by selecting an option and paying $20.
Prior to this addition, your old Google Voice number would remain active for 90 days and then drop off your account. The limitation is that calls or text messages can only be received on the old number but all new communication through your Google Voice account will only show your new Google Voice number.
This really is a welcome addition and we are pleased to see Google make this option available to users. I would be very glad to see additional integration with cellular carriers such as the new integration with Sprint. The full details of this new announcement is available from the Google Voice Blog.