I'm a long time user of a huge array of D'Addario products. I use them every day for long hours sometimes. For the most part, I have noted a failure rate which is minuscule in the grand scheme of things. When I have had a problem, D'Addario's customer service has been exemplary - for years. That's pretty awesome considering they don't just make strings. They have a wide customer base to answer to and still mange to help folk with a superb quick turn around.
Nothing but good to say about @D'Addario UK And yes, in terms of disclosure, I do endorse D'Addario. I am (proudly) on the artist roster, but I wouldn't have accepted if I couldn't rely on them for my business needs. So, Thank you Adam and co, you are brilliant, give yaselves a pat on the back!
Now, I should really get on with writing this new album.. lol.. D'Addario don't do any anti-procrastination products!!