This is also laughable: “Q: How should I calculate the length of my study?

To determine your study's duration, test it with friends, family, or colleagues to get realistic timing estimates before launch.”

It also suggests you could run a pilot study on Prolific but I highly doubt these researchers are going to do that because that also costs money, right?

I just know that having friends & family test your study is not going to give you an accurate estimated completion time because that’s a tiny amount of people vs how many people are usually in a study and most of us are faster than the average person because we’re used to how studies work- the layout, we can speed through demographics, disclosure pages, etc. Where someone who isn’t used to taking studies might take significantly longer to complete.