Should I drive my'07 less with mileage over 100k?

Stat squirreling away money in anticipation of a HV battery failure.

$2100+ for a NEW HV Battery, if you DIY. There have been reports of PriusChat members not being able to get the online pricing by the dealers who sell online. $2100/24months = $87.50/month to save.

Another option would be to find dealer coupons for the biggest percent off a non-discounted retail parts purchase. Hooman Toyota has a regular 20% off, 1st week of every month; LINK. Maybe get your oil changed at a local dealer when it it cheap, just to get on their service coupon mailing list. Costco has 15% for participating dealers. I'm sure AAA has a similar program like Costco's.

Refurbished/Rebuilt HV Battery packs are less than new. You can research this yourself. Doorman is one option. The big auto parts chains is another, but I think they all get their HV Battery from Doorman.