Must R Packages Unload Dynamic Libraries When They Unload?
Normally unloading a DLL would be a good idea. The resources it owns, would be completely freed, and re-loading would not be an issue.
In R, there is the complication of the R environment, because even if a DLL is unloaded, there may be some knowledge left behind in the R runtime. In this case, the result may be that the re-loaded DLL library does not share the same inferred state as the R variables which are intended to understand the DLL state, and thus errors occur.
I think it would be possible for an R package (DLL and R code) to be safely unloaded, but it would be easier for you to leave the DLLs loaded, unless you find particularly heavy resource usage.