when do people replace their Traction Battery? (includes stats)

I have a 2009 Prius with 257K original traction battery
purchased it in 2014 at 27K
I used to get 45-60MPG usually
47-50mpg in town traffic at 47mph and
55-60mpg on the interstate if i keep it at 60Mph.
that was up to around 2016
I keep an excel file now of all the stats to track.

in 2017 i replaced the 12V battery and you can see my mileage started dropping at that point, the dreaded low ev state as discussed in the other thread.

so at approx. what MPG will I get the code to replace the traction battery? you can see my MPG drops a little every year and im down to 39.22mpg right now.

sorry for the skewed numbers, it all looks good in the writing section, just gets skewed once posted

..................................2016 ... 2017 ..... 2018 .... 2019 ... 2020 ... 2021 ... 2022 ..2023 2024
tot miles driven .....27185 .... 28888... 22887 ... 19743 ... 17323 ... 23864... 23870 .. 25904
gallons ............ ....... 503 ..... 718 ... 534 ... 484 ... 441 ...574 .. 591 ... 632
cost .................... 1037 ..... 1621 .... 1387 ... 1179 ...929 .. 1668 .. 2191 ... 2129
actual MPG ..........53.97 40.20 42.79 40.77 39.19 41.5 40.32 40.97
car est MPG ..... .... 46.92 .... 43.91 .. 43.49 .. 43.71 .. 42.33 42.2 .. 41.35 40.60 39.22
eng hours ..... ..... ... 451 ...... 539 ..... 403 .... 392 .. ...351 .... 471 .. .. 450 458
ready mode hours ....... 934 .... 1128 ... 842 ..758 .. 750 .. 999 .. 1031 998