How long does a converter last?

A quality piston converter is good for years of regular use — the failure points are the piston seal drying out and the metal trim ring loosening, both on a timescale of hundreds of fills.

Capacity-wise, a standard converter holds 0.5–0.9 ml: roughly 8–15 pages of medium-nib writing per fill. Daily writers refill once or twice a week and replace the converter itself closer to once a decade.