I created a blueprint derived from Actor. I added a variable called LifeSpan with category: Settings. Whenever I set it’s default value the game resets it back to 0.0 after compiling. I checked the inherited variables but it only had InitialLifeSpan.
Renaming my variable from LifeSpan to MyLifeSpan fixes the problem. Took me 15 minutes of debugging to realize that the editor actually silently resets my value back to 0.0 because it somehow conflicts with some hidden private variable from the Actor class I suppose.