I like to say:

- One hour of planning saves ten hours or programming...

- and one hour of research saves ten hours of planning.

You can also invert it:

- Ten hours of programming saves one hour of planning...

- and ten hours of planning saves one hour of research.

> - Ten hours of programming saves one hour of planning...

If the planning is done with 5 or more people in a meeting, there still might be some time savings...

The difference between DRY and YAGNI is experience. Both are predicting the future, and you can only do that by having watched code evolve.

What's that saying? "Once is a mistake, twice is a coincidence, three times is a pattern".

Having to write something once, just write it.

Having to write something twice with small differences, think about it.

Having to write something three times? Consider refactoring.