Cheers All,
IMHO backing is the norm and not the exception on MOST reels. As Wolf said one very rarely uses the entire spool of line and, by spooling 1/3 of the reel with dacron, backing does reduce the amount of line one has to replace. However; I don't use backing to save money on line: I use backing to save money on blown up reels.
I consider Islander Precision Reels to be amongst the best reels for salmon fishing. They are machined out of bar stock aluminum and are almost bullet proof. Should you ever talk to Barry (General Manager at Islander) he can tell you (or even show you as he keeps a couple on his desk) Islander Reels that have blown up due to no backing. The monofilament line has literally exploded the reels from within. Very similiar to the mahogany Petz reels many of the old timers will recall. So...if they can do that to a quality metal product they can do that to a Shimano 4000 (or almost any other reel you wish to mention). I have a couple of Shimano 4000's on board and they have backing.
However; one needs to think about why this occurs and the cure for this problem then becomes obvious. Monofilament has a high water content and, as such, provides a natural stretch to the material. Reeled in under pressure the line wraps around the arbour tightly. When it dries out it shrinks and exerts pressure around the arbour as well as laterally against the sides. Usually the sides blow out before the arbour. Putting backing simply reduces the amount of line that exerts pressure against the arbour and sides.
The cure is obvious. Enjoy your reel. Enjoy your day. Enjoy your fish but, when you are done every single solitary day, reel your line out and bring it in without tension. If you did this you would never have any problems with blown reels. Unfortunately too many forget, don't care or are too tired to properly look after this easy fix. It's like the old Fram commercial: Either you pay me now or you pay me later.
I split one Peetz reel in my first year of fishing (many years ago). That's all. I do use backing but I also ensure that I take care of my equipment and that includes taking the 3 minutes at the end of every single trip to ensure my line is not going to damage my equipment. I depend on it and, because I do, I ensure it is looked after.
Fishing Guide
www.invictuscharters.com
BC Outdoors Pro Staff
www.fishingvancouverisland.org