> You can beat the efficiency of 5 trits in 8 bits

The single trit packing is a commonly optimized DBNULL structure for booleans.

Bits/trit approaches the 1.5 asymptote, because that is the fundamental packing limit.

The trick is to use it when you have a trit to start with, like when you have a set which is a tiny bit over a power of two.

There are places where you end up with odd numbers in set sizes, for example when storing a poker hand.

Read Cactus Kev's trick[1] which I think needs a 27 bit section & optimizing it was where I first ran into trit packing.

[1] - http://suffe.cool/poker/evaluator.html