Bank notes stick around for a long time. Old ones take several years and at times even a whole decade to replace completely.
Pakistan is currently undergoing a similar change as old notes (those bigger currency notes) are being phased out and no currency notes from old times are going to be accepted anywhere in Pakistan, starting December 1st, 2016. Today is the last day to get them exchanged.
That said you may be wondering why change them in the first place?
Improvement in Design and Durability
State Bank of Pakistan (SBP) issued the new designs in order to improve security, durability and aesthetic quality of the bank notes. Old design banknotes will not be accepted by any bank after November 30th, 2016.
This applies to 10, 50, 100 and 1000 rupee notes of the older design. It is worth mentioning that even though other banks will stop accepting these notes after November 30th this year, SBP will continue to accept these notes until December 31st, 2021.
If you forget to get your old notes exchanged before the last date, you can still go to State Bank of Pakistan and get the notes replaced from them.
For reference, here are the old bank notes which will no longer be accepted starting December.
It is highly unlikely that you still have old banknotes lying around and it is hard to find them in every day transactions as well.
New designs for Rs. 5, 10, 20, 50, 100, 500, 1000 and 5000 were issued in 2008. Since then the 5 Rupee note has been phased out and replaced by a 5 rupee coin instead.
If you have old currency notes, today is the last day to get them changed at your local banks. After today, only SBP will be authorized to change them until the end of this year.