Mtn have slashed Beta Talk bonus validity from 7days to 3days. Beta talk still offers 200% bonus airtime on all recharges , but the bonus airtime will be valid for just 3days. Not 7days. To confirm this , we recharged #100 airtime this morning and we got a notification that the bonus airtime will expire on the 16th of July 2015 ; 3days from now.
As at the time of writing , Mtn has not released an official statement to this effect.