A quick word of warning that you should probably periodically check that your hertz.com profile is configured to "decline" Hertz Gold Plus Rewards points and is instead linked to your United MileagePlus account.
I just completed a one-day rental which I was expecting to earn UA miles and which -- according to the receipt I got when I turned in the car -- instead earned Hertz points. I checked my renter profile on Hertz's web site and indeed, somehow, the "accept Hertz Gold Plus Rewards Points" setting had been enabled. No clue how this happened; definitely not a change I made, and prior Hertz rentals credited to UA rather than earning Hertz points.
I did have to visit the Gold counter at the start of this rental to add a new form of payment (my linked MileagePlus Explorer card had expired), but not sure if that process would also have changed the points preference (wacky). I will write to Hertz now and guess we'll see whether this is fixable.