My P20 had it's bottom bracket re-threaded 4 years ago (by me) and has seen some extreme use and mileage and everything is snug as a bug... the P20 had a 72.5mm shell so I did not have to re-face it.

Since then I have repeated this procedure on quite a number of R20 bottom brackets, re-threading them and facing them down to 73mm as when you try to fit a 68mm cartridge and are looking to face the bottom bracket, you start getting into the chain stay welds which is absolute hell on tools.

I suggest that blue loctite is used when the cartridge is installed as this will ensure that the cartridge remains secure and it also acts as an anti seize.