I give these earphones two stars because the sound is really good, which has to be acknowledged.
The problem I have with them is that I have, just now, had to request the third replacement, for the same exact issue.
I keep my phone in my, generally jeans, pocket while I walk my dog for a daily total of around 6 miles.
The phone is an iPhone 5 and I have it upside down, so the cable can come out of the bottom of the phone. In each case, after a maximum of a few months, I have lost sound to the left earphone. In each case, a gentle giggle/push at the connection point between the cable and jack will re-establish a connection to the left earphone, but that is only temporary.
So, maybe it is a question of my size, relative to the size of the jeans pockets and the length of the jack, but the fact of the matter is that I am finding this connection not to be reinforced enough to avoid a loosening of the cabling inside the jack.
If you don't generally walk with your phone in your trouser pocket, wile listening to music, you should be OK, otherwise, you should consider the strong chance that you might have the same problem I have run into, too many times to be a coincidence.