This is not unusual, which is why LN Engineering designed the lower temp T-stat, which is a simple bolt on replacement.
Please take a moment and read the article by Charles Navarro as to why this could be a valuable upgrade. I will install one in my '02 S as soon as I have time and can figure out what to do with spent coolant. LB is correct, lifetime coolant doesn't forever, but there are other steps you can take to protect your engine.
http://www.lnengineering.com/lowtemperaturethermostat.html