Technically you will catch 95% of issues/data by only monitoring one end of a link. But you will miss out on error/discard information on the one end of the link and if we are talking about WAN links that could be real significant data.
Thanks i should have been more specific it is LAN switch links. As we can't afford to buy more licences it was all I could think of as it can save nearly have of what they were originally monitoring on the LAN. I have pointed out that if we need specific monitoring it can be done for things like you mentioned. Always good to keep a few licences behind for specific situations.
Appreciate your time,