Historically lenses and windows on many military production programs, are potted, often with less than theoretical athermal potting gaps. Actual gaps may vary by factors of 2 to 4 less than ideal for athermal potting. Yet these military systems have passed rigorous qualification tests and seem to work adequately. Are problems lurking in the extremes of cold or hot for which MTF measurements are not typically done. Are typical stress levels high enough to impact optical performance. This paper will address these issues.