isoprophlex parent
For some radioactive isotope probably. Uranium 235 half life is, what, > 500 million years? That would make iron significantly hotter. Normal Fe is effectively around forever.
On long enough timescales, the most stable thing in the universe is the iron isotope 56Fe. All heavier atoms will decay to 56Fe, and all lighter atoms will eventually combine to form 56Fe via quantum processes, even at zero temperature. 10^15000 years from now, there'll be iron stars comprised almost entirely of 56Fe.