The Buderus GB 142/30 is seriously oversized for most 1600' houses in CT. It has a min-fire output of 28-30,000 BTU/hr which could easily be higher than your whole house heat load at the 99% outside design temperature, which means you applied a modulating boiler to a load where it rarely (if ever) modulates. Ideally you'd want the min-mod output to be at MOST half your design condition load, then tune the outdoor reset curve so that it gives long modulating burns for max comfort & efficiency. (Even the GB 142/24 is probably on the big side for your likely loads. There are smaller and more appropriate boilers out there.)
If you have the place cut up into a bunch of zones and the heat emitters are low-mass fin tube you may even end up short-cycling at condensing temps, cutting into boiler life and overall efficiency.
All good heating systems start with a careful analysis of the heat load, zoning, and radiation.
So, bring on the cold, but observe the system behavior carefully- there will be some tweaking to do. As long as you can run it at low temp near min-mod without short cycling it'll give you the efficiency you're after. Should you run into a short cycling issue there are fixed to be applied that would still let you run in condensing mode and really get that 96% efficiency rather than have to crank up the temp and only get 87%.