The difference between retaining Hood and retaining her capability

Did a 1939 statement about needing Hood for fifteen more years mean she was expected to serve until 1954?

Possibly, but it more likely meant the navy needed a Hood-like capability through that period, whether from Hood or a replacement.

Hood herself had a reasonable chance of remaining in service until 1954 under the suggested planning horizon. The 1939 statement can also be read as a requirement to retain a Hood-like capability for another fifteen years. That would leave the navy a choice between retaining Hood and replacing her. It does not establish an unconditional commitment to the same hull.