If it's something that requires a tech visit then you may well get charged the full $95 tech fee.
Personally I have never had the service plan. I had a 625 die a few years back, it was replaced free with no shipping charges. Had a 722 drive die 6 or 8 months ago and had the same deal - $0 out of pocket for the replacement. I didn't have to ask for or push for the "free" treatment at all.
Your mileage may vary, but if it's been 6 years that's $400+ paid out that would cover a lot of miscellaneous repair/shipping/tech fees.