Am i just expecting too much?
^^^^^ Yes, 'expecting too much'. It is normal for the system to take a bit to drop the vent temps. The reason for the common (but unreasonable) expectation that you should have cold vent temps immediately stems from a misunderstanding of how the A/C systems works.
Your system is one giant 'heat exchanger'. You Aren't pumping IN cold air, you are REMOVING heat from the cabin air. This takes time. You will need several complete air 'exchanges' before things begin to feel very cool.
Also, the higher your engine speed and the more air moving across the condenser (read highway speed) the better the system will work. It is not reasonable to expect the system to work as well at idle as it will at higher speeds.
There are two things going on every time you activate your A/C. First (and foremost) the system is removing the heat load (and humidity) from the cabin air (via the evaporator). ONLY after the system has had a chance to remove the bulk of the heat (keep your system on recirculate) does the effect of having air from the blower motor across the cold evaporator result in cold air being distributed from the vents in an effective way.
I know the two notions seem to contradict one another. Yes, when you first crank up your properly operating A/C unit...the air from the vents does feel cooler than the ambient, BUT at this point if there were no air exchanges...it would never get any cooler. With each air exchange you REMOVE heat. The absence of heat is what results in what we think of as cooler temps. As the heat load is slowly removed the system works better and better (to a point). Eventually...the vent temps 'can' approach the temperature of the evaporator and at that point...yes you are now blowing cooler air across the evap and out the vents.
Sorry to labor the point but it is well for folks to understand that an exchange of heat (moving it from inside the cab to outside the cab) is what is taking place. You are not (can not) just 'pour in the cool' with respect to refrigerant charge or vent temps.
There ARE (sometimes) gains to be had by 'optimizing' the refrigerant charge. IF you have the time and inclination, you can adjust the charge and see where it works best (it might be a bit under or over the factory recommended amount). But if you have 40°F. vent temps at highway speed (stabilized system) I wouldn't mess with it.