Does that necessarily discredit these courses of action?

Yes, under the assumption that you only value things that future-you will feel the effects of. If this is true, then all courses of action are equally rational and it doesn't matter what you do - you're at null.

If you are such a being which values at least one thing that you will not directly experience, then the answer is no, these actions can still have worth. Most humans are like this, even if they don't realize it.

The way around it is to make a superhuman effort at doing the not-literally-prohibited-by-physics-as-far-as-we-know kind of impossible by working to make cryonics, anti-aging, uploading, or AI (which presumably will then do one of the preceding three for you) possible.

Well...you'll still die eventually.