When activating a Windows to Go drive, it is recommended to use the the KMS (Key Management Service) instead of the MAK (Multiple Activation Key) or volume licensing.
Q) Every time I plug my drive into a different host, it asks me to enter a license key.
A) The reason for this is most likely because the activation key that is being entered is an MAK key. In order to prevent wasting licenses, KMS should be used.
Q) I used KMS but it is saying my activation is invalid.
A) KMS activation usually lasts 180 days before it has to re-validate itself. This can be done by running the WTG drive on a host machine that is within the KMS network.
Q) I am planning to use KMS, but the host machines I will be roaming on will not have access to the network that the KMS is on.
A) When Windows is activated through KMS, it typically holds activation for 180 days before needing to revalidate itself.