take a look at alot of fast mustangs on youtube, banging gears HARD with stock t5's...there are a couple of tricks that really help t5's live longer that dont cost much
but the biggest thing is clutch setup (need a soft hitting clutch) and how your DRIVE...the second point i cant stress enough...about 75% of people who drive a stickshift DO NOT KNOW HOW and abuse the transmissions without even knowing it...drive smart, dont miss gears and DO NOT powershift, and it should live
My car isnt a beast, but its survived 9 launches at the track with wheelhop (which kills t5's) and broke the axle and driveshaft yokes... and dozens more on the street with the tires aired down, dumping the clutch at 5k off the two step....hasnt skipped a beat8)