What is the valid hours of return ticket of Shanghai Maglev train for The Bund Sightseeing Tunnel ride?

Well, I am a little confused about your question. Shanghai Maglev train just runs between Longyang Road station and Shanghai Pudong Airport. It doesn't travel to The Bund Sightseeing Tunnel . You may mean the speed train goes through the tunnel . The return ticket is valid within the operation time of the speed train.
You can go from the Bund to Pundong new area and visit Oriental Pearl TV Tower and Jin Mao tower to avail the return ticket by The Bund Sightseeing Tunnel train back to Bund.