Thanks for the help and responses, cabinetman, GeorgeC and Steve Neul.
The brads came with the DIY caliber Campbell Hausen compressor (Lowes). I'm not sure if stock brads would be considered quality or not.
Fortunately I did use some wood glue on the trim before bradding the trim to the house. I guess only time and weather will tell if it holds up. I'm also hoping that the exterior flat paint will hold up well outdoors. Sheen is suppose to add durability but I'm not sure if that means flat will flat out fail much sooner compared to something else.
Thanks, I'll stay away from spar over latex and consider simply painting a latex sheen paint over the flat if need be.
As for brad seating. My gun has a blind knob that supposedly allows you to set the depth of the brad. It's not completely accurate. I must admit though that I kept shooting it at flush level depth as I figured that it would keep the wood looking seamless after being painted over. With my gun, if I shoot it at a recessed/countersunk level, the head of the gun causes a dent in the wood along with a hole twice to three times as wide as the head of the brad.
So I guess my options are to either paint over the brad points that are flush with the wood and hope for the best that it doesn't rust through the paint....or, should I take the end of a small bolt and hammer it into all the brad heads until it countersinks the brad into the trim..then fill with putty and paint? I tried this on a few brad heads today. It's doable but definitely sloppy as it mars and damages the wood.
Thoughts? Thank you very much for any advice.