Yea, so pretty much every programmer needs to be aware of thinking about lifetimes. The classic issues are creating a local and then giving a reference to it,

Yea, so pretty much every programmer needs to be aware of thinking about lifetimes. The classic issues are creating a local and then giving a reference to it, to something much longer lived, or even undying. In that last case, if your doing it a lot, with no regard to the objects change in lifetime, your effectively creating a leak (I can guarantee you someone, somewhere, is making this mistake in js right now). Most collection strategies won't touch an object that still has a reference to it. The second issue that became really common when people stopped paying attention to lifetimes, is that many resources you may be using (file handles, db connections, etc...) have very different constraints than memory. So you have to be cognizant of the fact that even though something has gone out of scope, it's lifetime really doesn't end until the gc gets around to collecting it. This is the reason special syntax and functions, like "with" and Dispose had to be added to languages like C# and Java. Python with it's reference counting maybe somewhat less susceptible to this second issue than the others, but it's not immune to it. Finally in many cases being aware of object lifetimes and specifically manipulating them can get you performance speed ups.