[randallsquared]

A timescale of hours is not required for most of the AI-doom arguments; if it took a year, that would have a similar outcome.

[zamalek]

It's definitely not a requirement, it's just an example of how it could rapidly progress. Within the scope of the argument 1 hour is as plausible as 1 year - the main point is that it happens shockingly fast and continues to happen even faster.

[randallsquared]

Humans being humans, one year is not nearly as shocking, which could contribute to people actually considering the possibility.