[grayclhn]

Use data on how long it takes to complete “projects.” Or break the project down into your best projection of the component tasks and multiply “number of equivalently sized tasks” by “average time to complete that sort of task over the past X months.”

Regardless, “collect and use data from the past,” does not require a “completely steady state,” and is pretty easy to modify. I’d feel a lot better having a conversation around, “this is totally new, do we think it will take about 2x or 5x longer than our normal projects?” Vs “this is totally new, so everyone guess how many months it will take without looking at any relevant data on either past project duration OR the accuracy of your past guesses.”

When people talk about “estimating task size” they almost invariably mean some planning-poker version of the second. Especially in TFA where they bring up forecasting as a better alternative.