According to NoOne N Particular :
Not intending to throw water on this subject,

It's probably a good idea anyway... ;-)

I don't know where your are located, but if you are in an area with extremes
of weather, winter can lead to cracked tiles, plaster, piping and filter
components and these would have to be repaired. You might have to leave
your filter running 24 hours a day if the temperatures never get above
freezing, or you might have to drain the pool in the winter and refill in
the spring. All expensive. Fortunately for me, I have only had a very few
days where I had to leave the filter running overnight. Our winter weather
is mild and there are only a couple of days a year that go below freezing.

Speaking for the great white north, the type of pool makes a big difference.

Our pool has steel walls, contoured sand for the bottom, and finally
a vinyl liner. I'm not sure what this type is called, but they're
quite common these days. They're quite a bit less expensive than
most other types.

The huge advantage of these winterizing. It's simply a matter of
draining the pool below the skimmer/vents (about 18" in our pool),
blowing the lines, pouring a jug of non-toxic antifreeze down the pool
skimmer plumbing, a air bottle "pillow" in the skimmer throat,
and covering the whole mess with a tarp.

Not counting time waiting for the pool to drain sufficiently, it takes
an hour or two (plus time filling the hold down pillows for the tarp).

Ours freezes solid right down to the bottom of the pool, no damage whatsoever.

The steel sides can expand without cracking.

There's at least some ice on the pool from late November/early Dec thru to
as late as late April.

Still on the first liner after 20 years.

Opening up in the summer, however, is a real PITA. First you have to drain
all the water off the tarp (thru the filter into the pool), then you have
to drain some more. Rake leaves out. And more water. Dig out more leaves out.
Etc.

Finally you get to drag the tarp off. Hopefuly without spilling the remaining
frog water into the pool.

[We have a truly massive Maple tree right beside the pool which dumps one
heck of a lot of leaves onto the trap. Along with the rest of the forest
immediately nearby]

Smaller pools and/or rigid covers make it a lot easier.

I wish the previous owner had installed a smaller pool....
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.