There is a concern that running too cool will cause the engine to run more rich (choking), resulting in increased fouling, deposits, and unburned fuel getting past the rings (blow by) contaminating the crankcase. But I really don't think a 180' stat is too cold to cause any of that too happen on a meaningful scale, unless one lives in a region where it is cold most of the year. In hotter areas of the country, a 180' stat may even be a wiser choice as the daily temperatures approach or exceed 100', particularly those densely populated areas where one often finds themselves doing an average of 10MPH on jammed expressways radiating 160+ surface temperatures.
However, I do believe 180' is about the lower limit here promoting optimal combustion and proper mixture. I would neither recommend drilling a 180' or going as low as 160' if one is at all concerned about reduce engine life and poor fuel economy. Some people don't mind the trade-off if they believe there is a performance gain