That webbing looks fine, your just starting to break it in.
The most common reasons I've retired webbing are, UV exposure, fraying from sharp objects(usually rocks, or damaged rings/carabiners ect), soiled beyond cleaning,(usually tree sap) and occasionally burns from friction(unlikely to be seen in hammocking).
UV exposure is the hardest to judge b/c it is based off the look and feel of the webbing, I generally pull it from service when it has faded noticeably and begins to feel less pliable.
Sharp object damage can take many shapes and forms but generally it will have to have penetrated into the core of the webbing to really damage it. (light fuzzing is normal when using rings in a friction setup)
Soiled is obvious, it will usually be heavy tree sap that has soaked into the webbing and cannot be cleaned out with simple dish soap and hot water.
I have seen a candle lantern cause a burn on hammock webbing, but doubt you'll see friction burns while hammocking.
Images courtesy of Slackline Express
(<these guys routinely use lots of webbing in their rigs)