Mechanical sympathy is great - and it's free!
I have the stock box, with a pretty short short shifter (10mm from in 1st gear to in 2nd gear), redline lightweight (smurfs blood) - been in the car since i bought it in 2005 and no issues. It even has a solid centre triple plate against it, and a 3L making decent power.
When it blows, it will be the 3 speed kit, with input shaft and the centre plate.