I know the feeling!

Cutting our yard in :30 minutes and 1.5 hr to trim was not making since with lots of concrete the issue.

1. I used a Sears Electric trimmer 1972–80 and can not remember the line breaking once. The cord and weather encouraged me to use a donated gas WeedWaker and Green Machine about 1982-02 (too short/heavy).

2. The weight encouraged me to get an Echo SRM 210 in 02. I c/n master not too much breakage per trim.

3. I decided I needed a Straight Shaft Hard Blade Trimmer mainly and converted my Echo SRM to that.

4. With Plenty Echo Power Heads, I now have the hard Blade, String, Split Straight shafts and Round-Up.

5. The Hard blade is my Work Horse at an angle (1 hr) vs straight allows trimming every 3rd 30:min cut.

6. The Round-Up and String allows touch-ups in tight areas flat vs soil erosions.

7. The Split shaft is string only back-up now but will serve as hard when I "find" that attachment. LOL!

8. I modified/trimmed the Hard Blade Attachment to resist holding damp dirt and added a larger clear Lexan Plastic Guard.

Try soaking your line in water for 48 hours before using it.

Soaking in water makes the line more flexible. It will last longer because it breaks less frequently. In some cases a lot longer. I was using some old line in my trimmer. There is no feed, I cut eleven inch pieces and mount them in the head. I was getting five or ten minutes out of a strand. After soaking in water for a few days I now get 30 to 60 minutes out of an eleven inch piece of string. Some manufacturers recommend soaking in water. Oregon makes that recommendation.

Soaking just before using, or soaking as soon as you purchase? Does it need to be wet when spooled on?

Good questions. I don't know the answers. It's easy for me because I don't use a spool. I store a dozen cut strands in water and then use as needed. They don't have to be wet when used so spooling on dry would be fine. Sometimes it takes me a couple of days to use a strand so the affect is good for a couple of days but for how long after that I don't know.

Google search "soak trimmer line in water":https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=soak%20trimmer%20line%20in%20water

Trimmer line gets brittle with age and soaking helps restore the flexibility. Buy smaller rolls more frequently and soak overnight if it sits on the shelf for more than a couple of weeks.It doesn't need to be wet to spool on.
I have experimented wit line and like Echo Crossfire the best. It feeds smoothly without welding, it is aggressive and wears well.

Somewhat off the OP topic but would cold weather like storing in an unheated shed make the line brittle? The line I left on the trimmer all winter was gone in a few seconds---literally. The line I put on after, that has been in a heated space, has stood up to much more abuse. Just a thought.

Try this trimmer line manufacturer from China, http://www.weedtrimmerline.com/ All kinds of trimmer lines in good quality and competitive price.