Having read all the posts on this thread and many more like them, I thought I might add a little insight as someone who strips and repairs these motors on a daily basis.
The Bosch seal for the main motor bearing does go some way to stopping water and dust entering this bearing, but you must replace the grease regularly. (How regularly will depend on the amount and type of riding you do and the way you clean your bike). Yes I agree Bosch should have sealed this motor better, but this motor was conceived for road bikes and performs fine in that environment. It was the bike manufacturers that decided it would be fun in a mountain bike. Not that I am sticking up for Bosch here.
Degreasing your chain on the bike won’t affect the main motor bearing. Most degreasants are hydrocarbon based and won’t wash silicone grease away (silicone wouldn't make a very good gasket sealant if it did). But, if you do clean your bike or degrease your chain, keep your bike upright so that the water / degreaser does not pool around the bearing.
There are two other bearings that you are forgetting about. The right-hand crank bearing is just behind the circlip that the crank arm sits against. If stiffness or stickiness of the crank is felt, it can be this bearing. You can and should also pack this area with silicone grease. You can also put a smear on the left-hand crank bearing.
Once these bearings have been protected, you can quite happily ride through bogs and streams without fear of ruining your motor. (obviously totally submerging the motor will still be a bad thing.)
Bike shops rarely have the press and equipment to undertake full bearing changes on these motors and Bosch will not sell them the bearings anyway. Yes, you can buy the main motor bearing anywhere, but you or your Bosch dealer cannot buy the crank bearings. They are a bespoke size and not available on the market. This is why we had to have them made!
As for warranty scares. There are no security seals on the right-hand side of the motor and the sealing strip is re-usable. If you are careful, I would challenge any dealer to know that anyone had been in there. It’s the same with tuning dongles, there is no cleaver electronics to tell anyone that one has ever been fitted so as long as it’s removed before going back to the dealer, there will be no problem. (Obviously, I’m not suggesting you fix your own motor outside of warranty but if there is a circumstance where you absolutely have to, it could be done.)(I'm not suggesting you fit a dongle either)
Above all, don’t be afraid of puddles and enjoy your motor! If the worst does happen and you’re out of warranty, then at least your motor can now be fixed and normally for less than the price of a new rear cassette.
https://performancelinebearings.com
There are some before and after photos below
Hope this helps you all get a few more miles
