Our "new" 1957 home has most all of its original wiring and an updated breaker panel. With only a few exceptions, the main circuits are all 14ga 2 conductor wire with a braided sheath running to metal boxes. This means most of the circuits are not grounded. I have already installed GFCIs in the kids bedrooms for some added safety.
As we start in on our remodel with insulation, wallpaper removal, a new closet, etc. I'm asking myself if I should bite the bullet, rip out all the drywall, run all new electrical, insulate, and install new drywall, or if I should blow-in fiberglass or inject foam into the walls with the drywall up and leave the wiring alone. The bathrooms have already been re-wired on their own circuits with 12/2 grounded romex. The kitchen will get gutted to the studs sometime in the future and get new electrical. So we're only talking about the bedrooms, living areas, and general lighting here really.
As I think about this, I wonder if there is really much value in replacing the wiring. First off, it isn't knob-and-tube and the wiring is in good shape and was installed well originally. Second, a grounded circuit is only beneficial to the inhabitant if the device plugged in is grounded, and honestly, most are not. Laptops, lamps, phone charges, even large flat screen televisions - all 2-prong plugs. There is some added safety to the electrician working on the metal boxes if those were grounded, but that would be me, and me isn't who I'm worried about there. Third, the main value the grounded circuit brings is to avoid energizing the body of a device. Having added the GFCIs, even though the body of a device could still become energized, no significant damage could be done to an inhabitant before the circuit was tripped. While the GFCI would not protect from injury should an inhabitant insert themselves between hot and neutral.... a grounded outlet wouldn't help protect against that either.
Finally, let's talk load. One major motivation for replacing wiring had typically been load. As I already said, the bathrooms and kitchen will get new circuits, so hairdryers and 8 bagel toasters are covered! As for the rest. While it used to be that modern living added a lot of load to the lighting circuits as we add can lights or install higher wattage bulbs... by using LEDs we can increase lumens by 5 times or so before we start to increase the load on those circuits. As for the devices we use, they are becoming more and more battery powered (phones, tablets, laptops) and those that are not are using much less power than they did even 10 years ago (LCD/LED screens instead of CRTs, laptops instead of desktops, etc.).
So with that, my current thinking is that there is little to no value in replacing all the wiring with 12/2 just to add a ground and increase the amp rating to 20A. Where I do need grounded power, such as my office, the media centers (debatable) and the garage (big power tools), I can run a couple dedicated circuits. Everything else.... I think I'm going to leave alone.
Anyone care to challenge my logic? Have I overlooked something?