When did you last check the cabin filter? It is a pain to get to in this car so it could be that it hasn't been changed and is clogged?
On mine, when the thermostat went bad it would take forever for the temp gauge to move and once it got warm would drop again if I drove over 25mph for any length of time. This would lead me towards something in your heating system and not the thermostat if your temp gauge is "normal".
On mine, when the thermostat went bad it would take forever for the temp gauge to move and once it got warm would drop again if I drove over 25mph for any length of time. This would lead me towards something in your heating system and not the thermostat if your temp gauge is "normal".