I was wondering the same thing myself actually. My NA6 has 177,000km on it and still has the original shocks. I read somewhere that shocks last about 100,000km. But then I spoke with a few more experienced guys at the supersprints, and they reckon that unless they're leaking fluid (which mine are not), there's not much to be gained by fitting new ones. Mine still damp OK, and their only "problem" is that the old boot covers have completely perished (bump stops still OK). I've got a new set of boot covers (thanks slub_dub!) which will go on when I get around to it.
My Wakefield PB is now down to 1:17.00 on RE001s and 1:15.85 on RE55s, so there's still a few seconds you should be able to find with your car. Hope to see you at the next club trackday on 24th October.
If you're looking for something to do to optimise your NA6, I'd suggest the following:
1) An aggressive wheel alignment. Mine is set up with zero toe front & rear, -1deg front camber, -2deg rear camber, 4.25deg castor. It feels great, even on everyday driving.
2) Ignition timing. Armed with an automotive multimeter (to set the idle speed), a timing light and paperclip, it takes five minutes to set the timing to 14 degrees for optimal power output. My NA6 put out 71rwkW on the Mania dyno which was only a few kWs down on NA8s with stock timing. It also ran without pinging on 91RON. For everyday, I now run on 95RON since NAs are not compatible with E10, and top up with 98RON for trackdays.
3) Tyre pressures. I usually aim for 38-39psi hot in RE001s. Get yourself a cheap infrared pyrometer from one of the countless Chinese vendors on ebay. It's handy to check the temperature profile across each tyre face after a track session. You can then tweak the pressures to try and smooth out the temperature profile. With stock camber you won't get it perfect - the shoulders tend to get cooked.
4) Swaybar bushes. Mine are loose and creak badly. I'm getting them all replaced very soon. Keen to see if they make any difference to laptimes. To be honest, I'm not expecting to be any quicker, but it should feel a lot tighter.