Andrew Gabriel wrote
Uncle Peter wrote

A woman just told me she had her house rewired because
it hadn't been done for 30 years. Have you ever bothered?
I mean if it works, why not just leave it? Wire doesn't rot.

Cable:

At 30 years old, it will be PVC cable.
Life of PVC cable depends on running temperature. At max
running temperature (70C), life is estimated at 22 years.

I doubt any of mine have ever got anything like that even
with the stuff that runs in the very hot roofspace. 50C maybe.

However, at room temperature, standard PVC cable life
is estimated at just over 1000 years, and most cables in
a home spend most of their time at room temperature.

That's not true of the stuff in the roofspace.

Accessories:

Wiring accessories (sockets, switches, consumer units, lampholders,
etc) generally have a life of around 30 years. That's not to say they'll
all die at 30 years old, but the first ones will start deteriorating by
then,

None of mine have and they are all over 40 years old now.

and you should consider an extensive inspection of them
all to ensure any are replaced before they become unsafe.

That is a separate issue to rewiring.

You might take the opportunity to change all the sockets and
switches to a more current design, and so they all still match.

Accessories which handle high currents (such as electric showers, hobs,
immersion heaters, etc) can age much more quickly, and in the process,
can generate local heating at the cable terminations which rapidly ages
the cable there too. These should be checked more often and high
quality versions chosen to give best life of the installation as a whole.

Don't get that with any of mine and its an all electric house too, no gas.

Design:

The design of a wiring installation will become
outdated as it increasingly fails to meet current needs.

I designed mine right in the first place. The most I have
done is screw some 8 or 16 outlet plug boards to the
wall in some places like on the kitchen benches now
that we have a lot more plug in electrical devices like
bread machines, microwave ovens, convection ovens,
frypans, etc etc etc than we did when I designed it
45 years ago.

I still have the wall oven plugged into a power point
just because I can't be arsed to wire it in properly.

In my parents' 1950's home

That's a lot more than the 30 years being discussed.

(which was wired with a ring circuit and 13A sockets, fortunately),
the standard was one socket per room, with 2 in the kitchen. They
had to pay £1 for any extra sockets installed during the build
(they paid for 2 extra in the living room).

In early 1960's, the Parker Morris report on standards in council housing
was published, and recommended an increase on things like sockets.
Although it only applied to council housing, the result was that council
houses of the early 1960's were better quality than most new private
occupier houses of the time, and the whole housing industry quickly
adopted much of the Parker Morris report in order to catch up.

Nowadays, rooms will often have 12 lights, as many as 10
sockets (and nearly all doubles, not singles), with a cluster
around the expected position of the entertainment centre.

Its better to have a plug board in the entertainment
center and plug that into the wall socket.

This is a far cry from a 1950's home, which although
the wiring is probably fine if not abused over the years,
original accessories will be well aging, and insufficient
sockets if not expanded over the years.

So there is no one answer. It depends...

That original 30 year rewiring question doesn't.

The only time that would be warranted is after a fire.

Not usually even after a flood.