If I understand your question correctly, yes, each access token will work for any number of requests until an hour passes, you will then need to refresh the token.
Thanks Tommy. This clarifies. I was thinking that once the latest access token A3 accessed, A1 become invalid. Per your answer, all the tokens A1, A2 and A3 will work until they expired and each can be refreshed with their own refresh token R1, R2 and R3 respectively when they expire.