The blades will have the Tersa logo and name plus the grade of blade stamped on them. If in doubt give Woidward a call. They are extremely helpful and knowledgable.
The finish will deteriorate from a glass finish fairly rapidly, as with all things, running at the speed they do the finest of edges dulls a little faily quickly. However, what is important is the amount of power or effort that you require to push the boards through. I can only describe it as you 'know' when they are too dull because the effort to push through increases significantly and the finish falls off rapidly. The tone of the machine changes and sounds far more laboured.
Dirty timber will dull blades very quickly as will taking off large amounts off at once.