A broken torsion spring gets replaced in pairs even if only one failed - the other one from the same 2002 install is on the same clock and close to its own limit, so replacing just the broken side means a second call within a year or two. Cables get checked and usually replaced at the same time, since they're cheap compared to the labor of coming back out for them separately.
If rollers are the issue - grinding, binding, a door that jumps in the track - we replace what's worn and check the track alignment, since original builder-grade track on a 20-year-old door has usually shifted slightly even if nobody's touched it.
Opener failures are a different call. If the motor or board on a 2002-era chain-drive unit is dead, we'll tell you straight whether it's worth repairing or whether a new opener is the better money - parts for openers that old aren't always stocked, and we're not going to chase down a board for a unit that's going to fail again in another system next year.