Never folding charts, is an ideal condition that most of us won't be
able to adhere to .... the main reasons being reduced longevity due to
tears along the creases and possible loss of features.
A couple of other things you can do to help save your charts.
If you use specific routes along a chart and you draw course lines for
these, use scotch tape over the course lines so that frequent erasures
of plots, don't destroy the chart, and never use "pinpoint" dividers
when plotting, to avoid punctures.

otn