I never fill the spool all the way with braid - no need to waste money like that. I use cheap mono as a backer and I top it with 75yds (1/4 of a 300yd spool) of mono. The "bottom" part of that braid doesn't get used or see UV light. So, when the top part is starting to get frayed or I suspect UV light has weakened it then I go out to the yard, tie the end to a fence post, walk out unspooling until I get to the mono/braid tie, cut, then retie to the now "old" end. This doubles the lifespan of each section of line.