The only times I’ve been spooled or seen clients spooled it’s been due to outside physical forces aiding the fish and against the angler. Last year we had it happen twice, once while in a boat on a lake that the wind was ripping across so hard I had to stay hammering at the oars just to keep us straight so we could ride the waves without tipping, and once while wading a super high river when the fish swam straight into a class five rapid and kept on going with the current at his back. The first one we finally lost, the second one, amazingly, we landed after an embarrassingly Brad Pit like near drowning experience (no clients were involved in this latter episode). Basically other than those types of conditional events though, it never happens. I do use larger than normal reels and keep plenty of backing on them all the time, but for the most part trout and salmon, even the really big guys, aren’t going to spool you. Backing on the other hand, we see a lot of down here, so it helps to keep that stuff fresh.