factors that will matter:
- what ink system (plastisol, waterbase, discharge, hsa, solvent) will all have different characteristics
- emulsion type
- emulsion hardening
- mesh type and manufacturing technique
- initial screen tension -- was it in the manufacturers suggested range or outside (above or below) of it.
- are you looking at 1 color or multicolor (shouldn't matter, but a single color 'screen' will likely last even longer than a multicolor due to the fact that screen tension isn't quite as important)
- off contact
- printing technique -- are you printing and 'dragging' the mesh with a squeegee at 100 psi, or are you stroking at 15 psi.
there's probably even more.
I've heard stories of 180,000 waterbase prints on a set of screens before... and the people telling the stores I trust and believe.