PF jars, like other colonizing jars, should be kept in a warm (75 - 85?F), dark place that is not too dry (target RH from 50% - 70% rh). The dark allows for the mycelia to colonize the entire cake without being "told" to pin (mycelium pins when introduced to light, reduction of CO2
, temperature fluctuations and lack of non colonized substrate). You don't want the cake to pin before the entire cake is colonized, otherwise you may have to prematurely birth the cake and risk contamination of the non colonized substrate, or leave a growing fruit inside while the rest of the cake has not been completed yet. You don't want to store the jars in an extremely dry area, since the water in the jar can evaporate into the air through the small punch holes in the lid.
A too humid environment can cause molds growing on the outside of the jars and possibly spreading into the jars, so don't go with the humidity over 70%.
This table from TMC illustrates the impact of temperature on the growth rate of mycelia. (The entire caption reads: "Figure 63. Chart showing influence of temperature on the rate of mycelial growth in Psilocybe cubensis
and Psilocybe mexicana
. (Adapted from Ames et al., 1958)."