The manual recommends a low threshold of 10% below and a high threshold of 20-25% above your target pressure.
Thus, for our 110PSI tires (on the RV), we have a low of 99 PSI and a high of 135 PSI. We left the high temp setting at 158 degrees F.
When traveling, it's perfectly normal for the pressure to get into the 120s. In the summer, on the sunny side of the RV, we've even seen 130.