If you're trying to point out that the Earth is finite, although you are correct, the scale is... large. Everything that decays via alpha decay ultimately makes helium.
Not to mention that a) worse comes to worse, we can always make our own, and b) it's literally >20% of the universe's (baryonic) mass.
The question is whether it's economic to use, not if it will run out.
It's only a reference to what was implied in your post. Nothing more.
a) Even though you may be able to decay the entire Earth into helium, it is only produced at a constant rate. If the rate of use is higher than the rate of production, you will still run out.
b) Which we have 0 access to.
c) You won't be able to always just "find other sources" of finite resources (I'm thinking more than just helium [unless you plan on becoming a pure helium lifeform]) and the Earth will become uninhabitable long before our resources are exhausted.
a) Not true. As I said: worse comes to worse we can always make our own. Alpha decay can be induced with particle beams, etc. Now, it's horridly inefficient, etc, etc. But it's possible.
b) What don't we have access to? The rest of the universe? True, for now. However, we don't "even" need to go interstellar for it.
c) No, we won't be able to forever. However, the thing is: with helium at least, the sources known now are sufficient, in raw quantity at least, until so far in the future that good luck predicting what our needs will be. It makes someone before the rise of automobiles calculating what the horse manure removal would have to be in 2100 look shortsighted.
What is 'sufficient'? How long a view are you taking on this?
With small percentages of natural gas containing helium (0-7%), much of what's currently coming up isn't being captured or is only now starting to be in Qatar and Russia. The rest is just let go, and once helium get's into the air it's over.
Luckily, as you suggested, prices going up means people are starting to build helium recycling systems. However congress made them artificially low and thus speed up unnecessary wastage of this precious resource.
If you're only concerned about the next 200 years, can you imagine if that was the same attitude in the 1600's? What would we have now?
Now imagine if we really are all flying around in giant helium aircraft because oil has run out or is too expensive... how much helium is getting used up for that purpose alone? There's far more natural gas/oil than helium.
If you're trying to point out that the Earth is finite, although you are correct, the scale is... large. Everything that decays via alpha decay ultimately makes helium.
Not to mention that a) worse comes to worse, we can always make our own, and b) it's literally >20% of the universe's (baryonic) mass.
The question is whether it's economic to use, not if it will run out.