Paint chipping too easily on trim and jambs
Chipping is not a problem of the finish (gloss, semi-gloss, or flat) of the paint. It's a problem of (lack of, or incorrect) preparation of the surface the paint is not sticking to. If the actual application of paint is the majority of work in painting something, you're probably doing it wrong; preparation is the majority of the work, and what the result depends on in pretty much all cases. 

Your pre-primed trim may have been exposed to a number of things in its travels between priming at the factory and you putting it in place - those surface contaminants need to be removed. This might involve washing/rinsing it (and then letting it dry fully) as well as sanding it.

Giving truly adequate drying/curing time and conditions before exposing to abuse is also a factor - humid air (given your location and the season there being summer) can drastically affect paint cure times, and "not coming off on your fingers" (i.e., surface dry) and "fully cured" are two very different states, with the "fully cured" state taking considerably more time to arrive at.