Coolant leak on W2 heads

So I am confused ... if it has been on the road for 1200 miles it should have been through many heat cycles already. Whats different about this heat cycle ?
I cant answer that definitively. All I know for sure is that randomly the leak began after two years of use, while the car had been parked and not started for a month and a half. Now after driving it a couple of times the issue has not presented itself again. I'm not saying whatever the issue is, that it is resolved. Currently the leak has stopped. For now the plan is to closely monitor, and use the car. Our season I so short here i would like to use the car providing i am causing it no harm. If the leak returns, the heads will come off.