There was some discussion in the past about this topic for any plugin, not just for pluginR. And some devs were against it. However, I still think that this option should exist.
Can you raise this topic through the devel list, please?
Technically, I have no clue how/where this should be changed in php.... but if generally agreed to have this extra option, then this can be added by some experienced developer (jyhem, for instance, etc).
P.S: This morning, I commited version 0.82 of PluginR fixing an issue with the cache refreshing, making shorter the inidication of cached R content, etc. (hidden in the icon on mouseover). It will be packed in mods.t.o automagically in a few hours/days, I guess.