Best if stored in dehumidified or air conditioned area.
Avoid knots in the monofilament – they reduce the strength.
Periodically inspect your handline for cuts or abrasions. The rope or
monofilament should be replaced if you feel the integrity has been
compromised. Under normal use these handlines should last for many years.
Of course events like allowing the line to get wrapped in the prop or driving
the boat over the handlines tend to cause more frequent maintenance
actions.