I was building an OAuth Server using the Microsoft stack of OWIN components and learned that it is not good to keep adding an indefinite number of claims to the bearer token returned by the OAuth Server. There is no hard limit, but if you create a bearer token over 2KB then you might start to see problems when using different tools. This started to happen in a software project I was working on when the number of claims created a bearer token over 4KB. A tool the QA team was using for testing started to have issues.
As a rule of thumb, I try to limit bearer tokens to under 2KB now.