In the first book, IIRC, they did not know that, and in fact believed the spheres would last forever.
The spheres were used like nukes, in a very indiscriminate way. Whole armies were sphered in a short time.
Many years after, when the first sphere popped, they realized a new way of time travel just opened.
Yes, till it got easy to make the bubbles. All you have to do to prevent being bubbled, was to carry a bubble. Doesn't prevent cutting you in half though, assuming they guessed the right half, so you might want to carry a few.
As far as I know, the book doesn't cover if the bobble retain their angular momentum or charge.
I always wondered if creating a bobble around an off-center weight would allow you to kind of spin it by wobbling it.
There were some places where large pieces of land unbobbled without any relative movement, so maybe they were locked in their rotation somehow?
I really liked that book a lot.