I've upgraded the secondary tenshioners but not the primarys. What's the worst thing that can happen if the primarys go? Please excuse the spelling.

 

The result of a primary failure isn't any different than a secondary failure. Engine damage possible. The biggest problem with the primaries is the cracking and breaking off of the long plastic slippers. Not so much the tensioner portion.
Most folks go with the secondaries only and get quite a large amount of mileage. I did secondaries and passed on the tensioners. Currently at 113,000 miles.

 

Thanks, I feel much better.