I don't think I've ever seen a notification from the Hertz app before but they're making up for lost time/and or they're getting particularly desperate for ancillary revenue:
Worth noting that even though they all reference the rental starting "tomorrow" the most recent one was actually about 10 minutes after I picked the car up (another
very nice surprise from the Hertz folks at Richmond -- i was pre-assigned a Cadillac XT6. For as awful as the employees at DC Union Station are Richmond more than makes up for it. )
I seems like they average about one every hour and started about T-24 from rental pickup time. Haven't gotten one since the "Hertz Gold Rental Agreement" email so hoping that whatever system was generating the notifications figured out that I have picked up the rental and trying to sell me insurance is moot at this point.