My mileage has tended to decline a little for various reasons, but I've done just over 6500 miles on my three electrics. The previous twelve years often saw much higher mileages on normal bikes with 5300 in a year as the highest.
On Arons bike faults, I've already given him my thoughts on the spokes, twistgrip, and slow motor reaction. I used to get loads of punctures on my Giant Lafree Light but stopped that permanently with Schwalbe Marathon Plus tyres. They do a 700c fairly fat one suitable for the Torq, they're pricey though. Fisher Leisure are the wholesalers your bike dealer can get them from.
The Cateye Velo 5 speedo is quite demanding about the sensor position, the alignment of your's could be the problem. The instruction sheet on that which came with the bike has an illustration of exactly where the sensor rod and magnet should meet, so if you adjust either the spoke magnet or wriggle the sensor rod tiewraps along to match that, it should be ok.