How long could the Vietnam War be delayed? With a POD whenever, how late could the war start?
Bonus points if it's in the 70's and you can detail the ramifications of such.
By Vietnam War, are you referring specifically to the time that U.S. ground troops were involved as opposed to "advisers"? I assume so; that's how most Americans see it.
The later the U.S. is involved, the more the Communists will gain ground. Given how corrupt, unpopular, and incompetent the South Vietnamese government was, they should be toast pretty quickly without the U.S. getting involved. I'd give it a couple years at best, unless North Vietnam is unusually paranoid about making a move for some reason.
Maybe if Diem survives longer, it could postpone the war. Ho Chi Minh and the North Vietnamese government thought that he was their strongest enemy at the time. (Wikipedia article citing a book called "Triumph Forsaken" by Moyar).