About Multiple Access Tokens

Given the TTL of access token is 60 minutes, what will happen that another access token was generated before the previous one expired? The scenarior could be that two different threads are running independently, one thread created one access token for calling APIs. 5 minute later, the other thread created another access token without knowing there already had access token created. Will both access token valid at the same time? Assuming both threads are under the same user credentials or from the same user accound.