Billet parts, what and when?

[Sleeper-6]

I'm planning on going into my trans after the new year and have a few questions on billet parts. When does each available part become necessary?
First thing that should be replaced is the forward drum, Next is the Imput shaft. After that I don't know.
In what order and power level/Mph do the rest of the parts become the weakest link?

 

[JDSfastGN]

forward drum is a must for anything in the mid 12s (even some slower cars have broken them) input shaft is around 11.90s and the OD planetary is one of the only other available billet pieces. Its a little strange as it can last forever or break in the 14s haha. If you have the money i would go ahead with one. high 11s in a heavy car may be pushing it although many have run them for years with no problems. Other than the normal hardened stator and good OEM sun gear shell theres not much else available other than a OD ring gear which i honestly don't know when they become a problem as ive never broken one or heard of one breaking. Good luck with the trans.