Is انقراض عصر necessary for a valid Ijmaa?
What this means is that do all the Mujtahid Imaams of a given time period have to die, after having agreed upon a given matter, for the Ijmaa to be valid or is the Ijmaa valid merely once they have agreed.
According to the majority of scholars if all the Mujtahid Imaams of a given time period agree on a matter, then Ijmaa has occurred.
A minority of scholars are of the opinion that it is not until these Mujtahid Imaams have died will the Ijmaa be considered binding. The evidence of the minority is that it is possible that anyone of these Mujtahid Imaams may change their mind and present a difference of opinion. It is only by their deaths can one be sure that they have not changed their stance.
The majority say that it is not possible for a given Mujtahid to change his stance becuase once an Ijmaa has occured then it is not possible for him to change his stance and go against the Ijmaa as it is binding now to adhere to it.