  We investigate ten years of user support emails in the large-scale solver
library PETSc in order to identify changes in user requests. For this purpose
we assign each email thread to one or several categories describing the type of
support request. We find that despite several changes in hardware architecture
as well programming models, the relative share of emails for the individual
categories does not show a notable change over time. This is particularly
remarkable as the total communication volume has increased four-fold in the
considered time frame, indicating a considerable growth of the user base. Our
data also demonstrates that user support cannot be substituted with what is
often referred to as 'better documentation' and that the involvement of core
developers in user support is essential.
