because I overlooked how much interest you can make on holding house money in accounts

They send you a 1099-INT. You just didn't put that in your 1040 form.

This year I started off with early payments and tried to track things more closely. Next year if our income is about the same I might just pay the safe harbor amount to avoid any surprises.

I tried predicting what my withholding should be for the first few years after retiring. Every year it was way off. One year too much, so I reduced it the next year. The next year was way way off in the other direction. Repeat, repeat.
Never got close to right. I either owed a whole bunch or got a huge refund.

Then I found out about the trick. The simplest way to handle it.
1) Figure out your Safe Harbor amount. The previous year's tax or 90% of this year's tax.
2) In early- or mid-December, take a withdrawal of that amount from your IRA and have 100% of it withheld.
This works especially well if you are taking RMD that you don't really need.
Or just an RMD like from an inherited IRA.

The first year I did this I was not 100% sure so I called the broker and talked to someone in their "retirement account department". He said, "Yeah, a lot of people do that. it's not a big deal. Quite common."