EMA C++ Developers Guide : 6 Consuming Data from the Cloud : 6.5 Version 2 Authentication Using oAuth Client Credentials : 6.5.2 Version 2 OAuth Client Credentials Token Lifespan
 
6.5.2 Version 2 OAuth Client Credentials Token Lifespan
Unlike Version 1, Version 2 will only produce a single Access Token, which will be valid for the length of the entire expires_in field in the token. This Access Token is used by the API to perform service discovery, and to connect to Real-Time — Optimized.
Once connected, the API does not need to periodically renew a token.
The API will re-request a token on reconnect, and will use that token for all reconnect attempts until a short time prior to expiry. At that time, the API will get a new token for reconnection use.