Just to give some slight optimism in opposition to your friends, I am soon to turn 41. Its harder, but it’s not impossible. Whatever you pursue, form is everything. Poor form cannot exist post 40. Technically, I am stronger than I have ever been, and yet I’m still falling apart. Don’t consider the number, just do the work, and do it well. Good luck to you!

You say “simply train,” but really, the training of these models is The most intensive part. Once they are trained, they require less power (relatively) to actually run for inference.