Sometimes you have to hit just the right combination of temperature and pressure for it to leak enough to drip down.
In your opinion it definitely has a crack then? It wouldn't just randomly spit out overflow right? I'm going to replace it then.
How old is the degas bottle?
It wouldn't randomly spit out coolant, but it could do so for a reason.
Some possible reasons:
Coolant grossly overfilled.
System not correctly bled.
Engine overheat for some reason.
Leak(s) elsewhere in the cooling system letting air in.
The bottle on this car is not an overflow bottle, its an expansion tank. It helps regulate pressure. Over time, it starts to leak air due to small hairline cracks. They get bigger over time until the bottle ruptures. Almost every LS needs the bottle replaced at some point.
Southern cars tend to suffer this the most, i guess due to higher temperatures. Its better to replace it for peace of mind. If the original bottle lasted this long, a new bottle should last about as long or maybe longer.
How about the other plastic cooling system parts in the car? When were they last replaced? What is the coolant level now?
So you haven't replaced the plastic cooling system parts at the front of the engine? I'd bet that's where your problem is now. (And yes, a small crack there could let air in, forcing coolant out through the pressure relief on the degas bottle cap.)
The bottle on this car is not an overflow bottle, its an expansion tank...
Look for traces of white coolant residue. I've had parts where if you looked really hard you could see the coolant residue, but you couldn't see the cracks from the exterior of the part.
Prime suspects are the tube that runs from the top of the engine to the thermostat housing and the upper and lower radiator hoses (plastic sections).