@principalmember
Thanks for the answers and a big thank you for posting tip no. 3 in the original post.

I have high property taxes and my county does allow me to pay one installment early. That’s going to save me more $1500.
I won’t have thought of doing this if I hadn’t chanced upon this thread.

Since most people will see a drop in their highest marginal rate in 2018, how does this strategy sound:
You overpay your 2017 state taxes by a huge amount, say $10,000. You deduct this from your 2017 federal tax bill at the high tax rate that you are currently paying.
In 3 months, you get that money back in your state refund. When you file your 2018 return, this will be taxable income. But you pay the lower 2018 rate at that time.

Do you see this working?

Even if the 1098 shows the extra mortgage payment in the 2017 year, what is the benefit? Isn’t mortgage interest still deductible in 2018?
Can someone explain where the saving comes from?

Are people trying to get the deduction this year because their tax rate will be lower next year?