Some conclusions can be derived from this data:
[*:3ll8kths]When a pouch can no longer decay any further, it is destroyed
[*:3ll8kths]The rate in which a pouch decays does not follow any geometric pattern
[*:3ll8kths]Each pouch is independent when determining the rate in which they decay (Using all 4 pouches will decay a Giant pouch at the same rate as if it were to be used alone).
[*:3ll8kths]The rate in which a pouch decays is based on number of essence put in said pouch, not the amount of clicks. Therefore, you could fill a Giant pouch 120 times by putting 1 essence at a time, or you could fill it completely 10 times.
[*:3ll8kths]The first values in which a pouch degrades remains constant (Giant is 120 essence, Large is 261 essence, Medium is 270 essence). Further decaying has shown to have a precision error of several whole numbers (Eg. Giant pouch first level of decay, or 75%/9 essence has shown to decay to the second level of decay, or 66.7%/8 essence, at either 18 essence [2 fills] or 27 [3 fills]
[*:3ll8kths]It is inferred that the reason Small pouches don't decay is because the decay value would result in only 1 essence being held, therefore making said pouch obsolete.