PLC, in my experience, the magnetic compasses on the etrex's is fairly inaccurate and worrying about magnetic north offset is not high on the list of the compass troubles. I would recommend if you enjoy the challenge of navigating by compass that you continue to do so with a real compass. I suspect you already have one, but if not, most high quality ones can be purchased for $10-15, which is far less than the Garmins.
I have found that navigating by graphical GPS map, with the map set to always point north, has relegated my compass to backup duty in the event my GPS fails completely.
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