I find this law only holds when you're doing something that is significantly new for you, and/or has many elements or individual components which can interact in complex ways and suffer from leaky abstraction effects.
But if you're doing just one thing. Or a few things. And/or it's a set of things/activities you've done almost exactly the same way previously, and knew how long that took, then no, this law does not hold, and sometimes things go faster or about what you expected.
Developing new software for clients and/or on top of new components, almost always is applicable however. Too many moving parts will bite you. Black boxes can bite you. Developing on the frontier, as opposed to walking along a well-trodden cow path, will bite you.
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I find this law only holds when you're doing something that is significantly new for you, and/or has many elements or individual components which can interact in complex ways and suffer from leaky abstraction effects.
But if you're doing just one thing. Or a few things. And/or it's a set of things/activities you've done almost exactly the same way previously, and knew how long that took, then no, this law does not hold, and sometimes things go faster or about what you expected.
Developing new software for clients and/or on top of new components, almost always is applicable however. Too many moving parts will bite you. Black boxes can bite you. Developing on the frontier, as opposed to walking along a well-trodden cow path, will bite you.