I see what you did there.

Yep, with any tear the "life time" for the boot is over!
With this position everything is a lifetime part!

On the issue of CV Joint itself, it will last the life of the car if dirt never gets inside.

This is because unlike the wheel bearings, the ball bearings inside the CV Joint slide along the tracks a bit here and there and not subject to wear and tear like a wheel bearings (which rotate all the time), and therefore the CV Joint will easily last some 400K.

I know a VW Passat owner with original axles at 400K because he simply replaces the CV Boots at fixed intervals, something like every 60-70K miles or whenever he spots minor cracks in the boots. This proves that if the CV Joint is greased and tightly sealed and never violated, the ball bearings inside last "forever".

The #1 cause of CV Joint failure is cracked boots, which must be fixed ASAP, i.e., within a few days, especially in winter (road salt) or when driving on dirt roads.

The problem with CV Boot is: once minor cracks develop, these cracks progress to full cracks very quickly, within a matter of a few weeks.

Anyway, my 2 cents...

FYI,

CV Joints and Boots for Euro cars (MB, BMW, VW, Audi, Volvo etc.) are made by GKN-Lobro...

Cn, agreed.

Problem is, the boots suck and have been known to break as early as 30k.

I'm at 50k and done them twice already. Always the front outers.

If they lasted 70k like your friend's, there wouldnt be much of a discussion on these.

Seeing that out of the 8 boots the car has only the front outers break early, and that the E70 seems to not have this problem, I think there was a design flaw on these that BMW fixed for the E70 and up.

Split boot
 

Has anyone used or found a split boot option for E 53?

I have to agree that E70 boot material has a different appearance, but the big improvement is having the extra fold between the two ends so any flex is spread out over four folds instead of just three. No doubt there's less stress on the boot.
I have been getting about 75,000 miles out of mine before they crack.

2002 X5 3.0 274,500 miles
2004 325i 119,500 miles

I have an update for this.
Spent some time with my indy yesterday, and he confirmed the following:
Starting with 2005 ALL X5 benefitted of a new rubber material for the CV boots. Unfortunately, BMW does NOT sell the boot separately, so the updated part is sold only with the front axle!!!. They have the same material as the e70 CV boot. Again, because the e70 CV boot does not fail, he could NOT take measurements of the CV boot, but he said by eyeballing the boot, the ID's look similar, only the e70 boot looks longer (due to the extra bellow). So it "might" fit. For now the e53 replacement CV boots are still made out the sh*tty material, only the original front axle comes with with updated rubber CV boot.

Wow Dorin that is a great update.

Wonder if you buy NEW axles from GKN Loebro do they come manufactured with the new material? Or only the BMW axles (OE part made by GKN I believe).

I did mine 10k miles ago so I have a while before they are due again but was curious.

I don't know. My indy told me that ONLY the O.E. part directly from the dealership have the updated CV boot. Which is a bummer if one experiences a torn CV boot......If I were you I would ask Loebro directly if they are supplied with the exact CV boot, or if they receive different CV boots if it's not a direct BMW order, and are meant for aftermarket supply.