Our original slide toppers lasted about 5 years. They had the same pinholes that you describe, plus they had frayed edges (small tears) and were very brittle. However, we are full-timers, and our slides are always deployed except when we are driving. Therefore, I would say your failure seems to be a bit premature, especially since you say the rig is stored indoors.
They are probably out of warranty, so you will probably end up bearing the expense yourself. The fabric can't be repaired because as I said above, it is probably also very brittle. Unless you can get some satisfaction from Dometic, I recommend Tough Top
slide toppers. The vinyl is heavier than the original, and I think the price is also lower than what is available from Dometic or A&E.