What's your EV/HV Pattern for longer trips?

Using 'B' when in EV mode going downhill is merely for convenience (less need for shifting pedals), it will not capture more energy (EV miles) than using 'D'+brake for the same speed profile.
Being on top of the hill in HV mode, you cannot immediately shift to EV mode anyway, 'D'+brake is best tactic until you can (or until the system shifts to EV mode automatically), and then - as convenient.

 

don't know where you get this from, i do this regularly in my Prime, assuming of course that the ICE is not in warm-up cycle. Beyond that, most of the time I do this, it switches to EV right away ...

 

I am speaking of the usual situation in long trips, whereby the car switches to HV mode after all EV miles have been depleted already when you are on the top and start descending.
If there are EV miles in the bank, like due to HV mode was manually switched to earlier, than of course you can switch back to EV mode any time.

From the manual (page 86):

■After EV mode has switched to HV mode due to low hybrid battery (traction battery) charge If the hybrid battery (traction battery) is regenerated by driving continuously down a long slope, the EV driving range etc. will be displayed on the multiinformation display and EV mode will be automatically switched to. If EV mode is not switched to even though EV driving range is being displayed, EV mode can be switched to by pressing the EV/HV mode selection switch.

 

In that scenario, agree ... me personally, I would (and have) avoid(ed) running EV miles to 0 (or - during a trip, only do that when close to charging ...

 

When in HV mode, no EV miles left, going down hills, it well shift to EV automatically. After a while it we'll show EV miles left. I got up to 12 miles coming to Mesa from Hartland, Wi.