Just reading boxrec.com and see that Ali beat Liston first time on 25th Feb 1964. His next fight was the rematch on 25th May 1965.

Till just now I never knew there was such a big gap between the fights and it seems a hell of a long lay off for a new champ.

Anyone any idea why there was such a long interlude ?

That's a huge lay off even by todays standards when fighters fight less frequently