When I used mono, I replaced every 3 months regardless of use to prevent too much memory development. I no longer use mono, I use PowerPro braid on everything, except the downrigger rods are the strike causes a horrific amount of tension and I use Big game on that line only.
Capt. Craig Copeland
2013 Nautic Star 2110 Shallow Bay Boat
Humminbird HELIX 12 CHIRP MEGA SI GPS G2N
Nautic Star Boats Pro Staff (nauticstarboats.com)
Redneck Fish'n Jigs Pro Staff (redneckfishn.com)