I'm still using the same Seaguar I spooled up in January (fishing nearly every weekend this year). Landed a 30 lb blue catfish on 12 lb test that bit a squarebill last weekend so it appears the line is still good to go.
For rods that get re-ties all the time (using Texas rigs and jigs in rocks, for example), I'll re-spool when the line on the spool gets so short that I can't make a long cast without getting down to the knot, and then I'll save that line for leader material. So, maybe a couple times a year on frequent re-tie rods. For what I pay for fluoro it d--- well better last that long.