Helium is semi renewable. More is constantly created by underground decay of radioactive isotopes. But we're probably using it up faster.
Regardless of helium supplies, party balloons are problematic because they tend to escape and contaminate the environment with rubber and plastic. I frequently see empty mylar balloons floating in the ocean.
Oil and Helium are both replaced on geologic timescales their effectively a constant in terms of human lifespans.
You can estimate decay rates from net heat generated by the earth, but only a tiny fraction of the helium produced is close enough to the surface to be captured by us. On top of this helium is really good at escaping confinement so you need very specific geological formations to end up with significant quantities.
Thanks for the correction. I ignored decay products because it is a very small rate. Anyway, if we're invoking physics, the Sun harbors a very large reservoir of He. ;-)
Regardless of helium supplies, party balloons are problematic because they tend to escape and contaminate the environment with rubber and plastic. I frequently see empty mylar balloons floating in the ocean.