The best answer I've seen after many discussions of this topic on another FIRE forum is to attempt to level your top marginal bracket across your lifetime.
One rough first cut approximation for this is to figure out what your top marginal rate will be when you are 72, given that you will be subject to RMDs, will be collecting Social Security, and will possibly face IRMAA surcharges. Compare that rate to your current rate, and it may make sense to take more now so that your tax rate from 72 onward isn't as high.
When leveling, it is also thought to be important to consider state income taxes, IRMAA surcharges, FAFSA EFC effects if you have kids who may be in college, and ACA subsidy losses. All of these things act like parallel tax systems. It can get complicated quickly.
There are software packages out there that can do the math for you. I-ORP is well-known, well-regarded, and free, although it can be hard to set up and understand and hard to believe the results. There are other packages which cost a modest fee that I've seen referenced but am not that familiar with.
Personally I'm converting up to a FAFSA-related limit this year and possibly next, then will convert to the top of the 12% bracket for a number of years, then eventually to top of the 22% bracket. At least that's the latest answer according to my homegrown spreadsheet and very simple approach. I'm still trying to get a handle on the whole thing, honestly.
