If you have logic to do a speed slow down on layers that print too fast, but you also have an ooze shield or a perimeter printing, it appears to me the shield/perimeter is not being taken into account as part of the layer. So what happens is the print goes slower and slower as the layers get smaller toward the top. This is expected on the part of the print that has the small layer due to the temperature cooldown time. What actually happens though is the shield prints at the same slow speed. The end result is that the layer actually takes far too long to print and the print time is unnecessarily increased. Depending on your print this can add quite a bit of unwanted print time.