Rear bearings fail very rarely. It fails usually when you load your car over the limit, drive on bumpy roads regularly or tow heavy trailers.
You need to change bearing only if it is causing problems otherwise do not worry about it. People have camries with over 200k miles and never change rear bearings.
Every 80K miles, 100K max.
I think they recommend to change it each 160-180K miles.
Well to begin with how often do you use your trailer? I recommend that you should check and grease your bearings every six months at the least.
With each brake job.
Every 90K miles.
Each 5k miles.
you should change oil on you car every 5000 miles
weekly
According to my dealer, it should be changed at 150,000 km.
Passwords should be changed every month.
weekly
When its old