Is moving a desk upstairs/downstairs for comfort twice a year a sign of poor insulation?
I have seen what in my opinion are crappy jobs on multi floor systems. No single system at the same static level year round will ever heat / cool properly. I install adjustable dampers in the trunk lines both supply and output for the air handler. In the summer the upper floors are wide open and the lower floors closed down ~20% this pushes more cold air up where it is warmer. In the winter I reverse for the lower floors to be open and the upper floors throttled back. This uses a limited amount of natural convection or heat rising cool falling because of the density. 

It may be possible to add trunk dampers this is the best and easiest way to adjust for summer winter temp changes , even a very well insulated home should have dampers in my opinion not only in the rooms and each room to be balanced but on the trunk lines to the different levels so the house comfort is similar on all levels.