Precompilation

I am using Atom with Julia v1.4; I keep my libraries precompiled at the beginning of the day and did some great work yesterday. This morning, after leaving Atom open overnight, I find that everything must be recompiled. In other words, for some reason, yesterday’s precompiled libraries are either somehow out of date, or Atom forgot about them. Has anybody experienced this behavior? It is really bothersome. Luckily, it only took 5 min to recompile. Thanks. Gordon.