New release: startup 0.12.0 is now on CRAN. This version introduces support for processing some of the R startup files with a certain frequency, e.g. once per day, once per week, or once per month. See below for two examples.
startup::startup() is cross platform.
The startup package makes it easy to split up a long, complicated .Rprofile startup file into multiple, smaller files in a .Rprofile.d/ folder. For instance, setting R option repos in a separate file ~/.