You'll find a lot of opinions from those that don't QT their inverts, those that QT for a few weeks/45 days, and those that QT for 76 days. It really comes down to your previous experiences and risk tolerance. For a great write up on the issue, check this post and decide for yourself.
The recommendation for shrimp is to go 45/76 days, or until first molt is observed (assuming you do not transfer any of the original water to the tank).
Coral/Invert Quarantine Time Frames Preface: The purpose of this article is to outline time periods required to properly quarantine (QT) marine corals & invertebrates. While unable to host ectoparasites the way fish do, corals/inverts are still able to “carry” fish diseases in one of two ways...