[gdp]

I don't think there's really such a thing as a "one-time project". It is very rare that you would create a piece of software in its entirety with no variation from your original design or conception of the software, and then never revisit or change it. As soon as you start modifying or maintaining software, you are in a position where your up-front design decisions may hinder your efforts to improve or add features.

[azzleandre]

"and that's why you never ..." :-)

With one-time projects I've meant products like a micro-page that a customer wants for some ad-campaign an then after some weeks have passed nobody will ever visit again.

But I agree, anything more than that is destined to be modified one day.