How often should you call?

[bigpooch]

Correct; nevertheless, it is still possible to call in
such a way that your opponent's bluffs in the long run
break even theoretically. In practice though, you may
just let your opponent make a small profit instead.
Also, for a more practical approach, as you stated,
pass the worst hands, call or raise with the best hands
and with the mere bluff catching hands simply use
judgment.

There is also another minor factor to consider in
hold'em (not just the fact your hand is sometimes in
a narrow range) and that is your opponent often has
cards that are the same rank as yours and therefore
the distribution used to call with will have to be
adjusted accordingly. So even if you could have one
of AA, AK or KK say, your opponent may more likely
hold an ace than a king so the above frequencies
would have to be a little different from the
combinatorially derived frequencies.