In article xwhRg.1082$Rp3.261@dukeread12, "new_CFI"
wrote:

as far as left/right/both/off, normaly you set it on both and forget it.
some planes have left/right/off, I alternate every 15 min.

Every 15 minutes? That seems a bit excessive. Once an hour should keep
things pretty much in balance. If you want to get fancy, do your first
switch after a half hour, then every hour after that.

On a long flight, keeping track of fuel is more than just mindlessly
switching tanks every so often. As an example, on a recent flight I took,
we started out with 72 gallons usable, burned about 16 gph in cruise. The
POH prohibits takeoffs on any tank less than 1/4 full.

We had about 3 hours to our destination, at which there was no fuel
available; we had another 1/2 hour hop to someplace with fuel on the way
back.

We burned one tank down to 20 gallons, then from the other one for the rest
of the 3 hour leg. When we had our destination in sight, we switched to
the fuller tank for the landing. We took off again on that fuller tank,
and switched back to the lower one most of the 1/2 hop to where we could
get fuel, then switch back to the fuller one again in the pattern and
landed on that. This make sure that on both landings, we were running off
a tank that was just a little under half full, so we wouldn't have any
problems if we needed to do a go-around. It also mean that if we landed at
our fuel spot and discovered we couldn't get any fuel for some unexpected
reason, we still had a half-full tank to take off on again.

Moral: I'd rather have one half-full tank and one almost empty one than
have two that are 1/4 full.