Sad, but it’s true.

I learned this the hard way, many old personal projects of mine got lost because of that. 😢 

 We stand shakily upon the shoulders of giants. 

 Yup. Vendoring dependencies helps. The underlying OS will change though, usually for the better. 

 Entropy in code is a good thing, there are only a few things that remain constant since Humans walked the Earth;-

The rules of the Universe;
Life begins;
Life spreads;
Life evolves and
Life that exchanges Empathy survives.

Code can evolve, currently by human intervention only.  

We need to be very very careful that code does not evolve without our intervention and particularly it doesn't evolve with exchanging Human Empathy.

Bitcoin is a prime example of code that exchanges human empathy and can be used to stop runaway Psychopath AI.

Perishable code is a blessing, don't play God and invent unstoppable code that's not Bitcoin or you'll learn to livE backwards.

:) 

 Runtime platforms are what perish. 

 Depends on the programming language and platforms. There's decades old (Common) Lisp code that's trivial to get running, if it even needs changes at all. 

 Checkout Nix. You can create a hermetically sealed environment independent of your OS. 

 Guys, can you imagine an Amethyst in 3 years.