My 1080 run since 5 Years and they have a higher core because lower temps.
So more hash, and it pays off.
On the power side you have a bit less power usage. Think about 6 or 6 gpus and each 3 fans,
adding a few fans for the case.
Watercooled i need only 3 Fans overall.
Besides, when you sell the GPUs the fans are brand new and thats a benefit too.