Not all file formats you use for storing your data will last forever. Applications like Word, Excel, Stata and SPSS, all commercial products come and go, or change drastically over time. To ensure that your files can be opened in an archive you’d best store them in file formats which are open, like plain text. Some programs, in general the Open Source programs, like R, do so automatically, but the commercial programs do not.
It is strongly advised to store your data, if possible, in open sustainable formats. The faculty uses the list of file formats of DANS.