I don’t think the battery is likely to need replacement in 5 years as you indicate. I think in the field they are lasting far longer. Mine is still doing great at 113K miles.
Very good!
Are you in a warm climate?
I heard 8 years is the warranty of the battery on the Prius, so they must expect them to last at least that long FWIW.
US model? It is programmed to only use the battery down to 45%, and not charge it higher than 65%, to optimize battery life.
Of course, this usage maximizes fuel consumption.