I've never heard it called "reboring" - wonder if there is a different procedure for when it gets really bad, but I'd have thought problems (backup) would happen pretty quickly, so wouldn't be too bad as long as you take care of it.

They basically use something like a weed whacker fed down the pipe, except it uses a short bit of chain instead of trimmer line, and will pulverise any intruding roots.

There are at least two techniques: sewer rooting (low velocity and high torque) and sewer de-scaling (opposite).