My normal cycle for movies is eighteen months and each part is separate.

Shyamalan is describing his personal creative and production rhythm: he typically needs about eighteen months to develop and deliver a film, and he treats the stages of filmmaking as distinct units rather than a single continuous blur. The remark underscores a disciplined, process-oriented view of authorship—suggesting that writing, preproduction, shooting, and postproduction each demand different mental modes and should be compartmentalized. It also implies a preference for steady, repeatable pacing over rushing projects to meet external expectations, and it frames his output as governed by an internal “cycle” rather than by trends or studio calendars.