The notion of infinity is 100% valid as a mathematical concept. Actually math recognizes more than one kind of infinity, if you want to look up aleph null and aleph one.

Then the question becomes: is math real or just an idea?
I would say that math is so gosh darned effective at describing and predicting reality that it's absurd to imagine that it's not part of reality. I'm not talking about our representations of math concepts; I'm talking about the physical relationships math describes so accurately.

But I don't have the energy to debate a big question like that.

It's an idea that exists.

Infinity, as in Algebra and Calculus is a real concept, with one caveat: it continues to increase with no bounds.

Can a lack of limitation truly be defined?

I think we should ask Einstein.

Look I know I'm old but I'm not THAT old

Its real