Sometimes the "low coolant" light REALLY means LOW COOLANT!

[G-Benz]

The W124 used to get false readings from the "low coolant" indicator last year. Coolant level was fine, so I cleaned the sensor and the problem went away.

Last night, the light came back on. When everything cooled down, I check the level and it was indeed, low. So I topped it off and things are fine. Appeared to be about a pint or so low.

Here's my question. Should I be concerned about having to top off the coolant? Engine temps remain at around 87C, even in the hot Texas stop-and-go traffic situations! No sign of any fluid on the ground, either.

Does this stuff evaporate over time?

Note: practically every cooling system component has been replaced in the last three years...but the head gasket is still original...