I have 293k on original traction battery. Should I replace?

We love our 2007 Prius. Original battery and 293k miles. Still seems to be going strong and getting 49mpg.
I used tech stream and looked at the voltage of the cells and they were all very close. ICE seems fine, although it does go through a bit of oil. I recently changed the trans fluid.

I've not noticed any signs of battery failure, except possibly this: On a long trip a few days ago, with 4 occupants, I think I noticed the ICE revving pretty high as I was accelerating up to highway speed. It almost felt like a slipping clutch on a manual transmission. I think this symptom went away as I drove. Yesterday driving the car seemed perfect.

I also was watching the info display and it seemed like possibly the ICE came on more readily than it used to- but this may have been me looking for a problem.

I would think that my mpg would drop as the battery starts to crap out, but it remains >49 mpg, like when we bought it.

I bought this car with 200k on it and figured on an after market battery pack, when the original finally failed. I wonder if it makes sense to wait for it to fail (and go for a world record), or just preemptively replace it, so that it doesn't fail at an inconvenient time?