Look at how much your lump sum for pension is decreasing month to month - mine is decreasing about $1000/month because it's one less month of expected lifetime they have to pay you for.
Also, the interest rates used to calculate the lump sum amount (set by IRS) get adjusted once a year. The rates went up some this year so my lump sum amount took a 2.1% hit. However, the Fed is talking about multiple interest rate hikes in the next year or so - if you wait until after 9/1/2022 to retire you will most likely take an even bigger hit.