I'll bet I watched a half dozen YouTube videos on this. One guy left a Pmag loaded for several years without the dust cover and it shot fine. Another YouTuber stated that if you store Pmags loaded the lips might crack if you don't store them with the dust/impact covers. The main issue supposedly is tension on the plastic feed lips over time. The dust covers are supposed to mitigate this.
I gotta be honest: from my join date until today I hesitated trusting Pmags as anything but every day range mags because of differing opinions on subjects like this.
I don't wanna Google it (again) and get 87 different opinions.
Once and for all: If one were to store 30-round Pmags loaded, whether filled to capacity or downloaded a tad--does one need to use the impact/dust covers to keep the tension off the feed lips?