Ive noticed that OEM tyres wear pretty quickly.

hehe I need to stop trying to activate the dsc on every corner, but i do like that flashing light.

does anyone know which tyre would be the hardest wearing? not necessarily the highest grip but which brand would last the longest.

 

They all vary -- check the treadwear rating on any given tire -- the higher the number, the better the treadwear, and (presumably) the longer the tread will last.

The stock RE040's have a very low treadwear rating of about 140, IIRC. Probably last from 8-15K miles, depending on how hard you hammer them.

The best maximum performance tires currently have treadwear ratings around 240-300.

I recommend you snoop around the tire info pages at The Tire Rack

 

140 rating equals 8-15 K tire life? Anything's possible, but that probably would involve a whole lot of "hammering" -- say, some track work.
The tread wear ratings are set by the manufacturers, and 100 is supposed to equal 20,000 miles. In other words, the OEM 18" RE040s are rated by Bridgestone to last 28 K.
Bridgestone -- and anybody -- would tell you that there is a wide range, depending on use/abuse. In setting the 140, though, they are not supposed to give you a rating that only works when you putter along at the double nickel. They rate the tires for 168 mph, and design them to go on a car with the capacity to generate high braking and cornering loads (moderate acceleration loads), which they know will be bought and driven by people who will use that capacity.
I don't know how honest Bridgestone is in its rating, but they should be saying that a person who drives vigorously on the road (I don't think they factor in track use, and they shouldn't have to for this purpose) will get 28 K, on average.
In a few years, we'll see what really happens.

 

actually my local potenaza tire dealer told me not to plan on more than 15k for normal use

 

I don't get my 8 'til next month, but I have been running Potenza RE910's on my Prelude for years. They have a treadwear rating of 400 and traction rating of A. They were a big improvement over the stock rubber and I have gotten very reasonable life out of them. Of course, I can't drive the Prelude the way I expect to drive the 8, and the RE040's are a lot softer, but long tread-life won't do you any good if you go sliding of the road into some imovable object.