I was not happy with the Stihl round trimmer line and tried Echo's Crossfire. Have been very pleased with it, it cuts well and does not need to be advanced as often.
Fence posts and concrete will destroy any line, rather than moving in right away try a slower approach so the line cuts with minimal contact with the obstructions.

You may laugh but when I purchased a Stihl FS-56 last year and had the same issue - I actually replaced the head with a PivoTrim from Home Depot. Solved my bump & feed issues.

I have about 200 feet of chain link, 50 feet of raised concrete paver bed and about 80 feet of a natural rock border I do in about 15 minutes at this point. No longer do I stop for string.

I do replace the string after each cut so I'm ready for the next time though. Since it only holds 4 or 5 (can't recall the exact number) it's totally painless.

For a small price and large payback on performance - it's well worth it.

I just use the Stihl stuff. No problems. Just make sure it is the correct width.

Bill

String Trimmer Line Cords can be a nightmare when trying to get your weed Trimming task completed. On going breaking trimmer String line cords and downtime can be frustrating when this type of issue occurs.

We gave up using String Trimmer Line cords in 2012 after we discovered a new Trimmer String Line Replacement kit called the Trimmer Genie String line replacement kit.

Now we have zero downtime and the new Trimmer String line replacement kit stops all flying debris and helps protect trees while trimming.

There is also another type of technology Trimmer String line replacement kit called ( Hover Trimmer ). While we have never used it, the benefits look excellent too. If you wish to turn your weed String Trimmer line head into a Stringless Trimmer and never have to worry about on going broken Weed String Trimmer Line Cords again then you should check out either of these new Trimmer Head applications.

Hope this helps you with the hassle of having to deal with Nylon String Trimmer Line Cords again.

Here is a link that might be useful: Trimmer Genie Reviews 2013