Is it necessary to upgrade your apps with new ad unit ID after upgrading to new admob

[Muhammad Humayoun]

I have recently upgraded to new Admob, Now do i have to update all my apps with new ad unit IDs?? As for one of my app, I have lost the keystore, so i won't be able to update it in future, but still that app has a very good no. of users which produce considerable amount of traffic and ad requests with the legacy id. 

[Venkatramanan]

As far as i know, you need not necessarily update the existing apps to get ads. The ads will be delivered to the old apps. If you need to update the application, then you need to use new google play services instead of the old one.

Regard,

Venkat.

[Eric Leichtenschlag]

If you've upgraded, you aren't required to update your apps with the new ad unit IDs. However, we do recommend that if you are updating your app anyways that you start using the new ad units in your next version.