The only time I sprung for a fixed price, fee-only CFP was with the pending birth of my son. I was perfectly fine managing things for me and DW, but it got to me that I was learning a lot of new things, and didn't want to screw up my adjustments for him.
The planner I found was great, and was open to my wacky idea of FIRE, even though he had no clients pursuing it before. He made some suggestions, but the planning was largely confirmatory. And that was great! He didn't have to agree, but confirmation of the steps I was taking was one of the two outcomes Inwas looking for.
I paid $1,200 for a full plan,, and had options for a continuing relationship for either a $400 a year retainer, or a discount price for a full plan of $800 in the next five years. I did not take up either offer, but I appreciated the flexibility if I ran into something else.
Nothing brings confidence like experience. If you are truly comfortable with your plan and how it's working, then you are good. I do think, for a competent and confident DIY'er, an outside professional opinion is best sought out when you have a significant life change. Maybe that is He death of your parents, if you inherit some complicated investments. (Or just investments that aren't in your wheelhouse) Maybe it's estate planning, if it looks like you will have a lot left over. A CFP may play a rol3, but a CPA (for taxes) or estate planning attorney might be the best choice.