Is there an upper limit for elements?

And if there is, I won’t be the one to have it.

Still, is there some way to determine if two particles are strong bonded? If I put two protons right over that distance (so they are not strong bonded), how long do they take to fly apart?

Define “apart”. They’ll start moving apart immediately, and (absent any other forces) keep moving apart forever.

And it should be noted that, if you do manage to make Helium-2, it’s not the electrostatic repulsion that tears it apart. The strong force can attract or repel in various circumstances (which are far too complicated to explain in a message board post, to the extent that they’re even understood at all), and two protons (or, equivalently, two neutrons) with nothing else in the picture are one of the circumstances where it’s repulsive.

Then I feel my question is even more to the point. Why do we think of He-2 as a something that exists at all? If there is never any bond to hold these two protons together but they are just fighting to escape each other, why do we ever think of them as a unit of some sort? What makes these two separate particles that want nothing with each other a nucleus?