So I have used DPPs pretty much since they became available, and have been using RMRs for quiet a long time as well type 1 & 2. For me as an everyday, all day concealed carry person and USPSA shooter they are dead equal in everything but battery life for my uses. I change the batteries on my DPPs every 6 months using Energizer batteries (awaiting internet bashing, something something Sage dynamics paper(whatever & double parenthesizes)) and have not had one kill a battery before that time frame that I can remember, oh which the top loading battery is super convenient. I use Dawson Precision co-witness BUIS for my carry gun and have had zero issues other then some minor holster fitting due to front sight height.
As for:
Anyone here use a DPP on duty? If so does it hold up and how is the battery life when being used 8-12 hrs a day.
Neither are being 'used' 8-12 hours day, just 'on' 8-12 hours a day, so that is an unfair statement; and as I have stated, my DPP that is carried all day every day doesn't magically eat batteries, just do routine battery changes. My DPP fits in the new Safariland 6390RDS with closing hood so that isn't a concern either. If the DPPs hold up all day everyday in my holster they then will in yours too and my USPSA gun/DPP alone sees about 3 matches a month + practice, and guess what, still works fine and holds zero.
I have had to send back more RMRs in the last 2 years then DPPs, 3 vs 1. 3 RMRs had electronic failures/issues (not battery related, actual electronic issues) and 1 DPP (by choice not necessity for a lens). My last encounter with Trijicon's service management left such a disgustingly bad taste in my mouth I sold my RMRs and never looked back. That encounter did not influence my decision on whether the RMR was good to go, just that I will never again deal with or buy anything Trijicon, the company, again I believe for mine & your uses the DPP and RMR are equal.