Pete,
What type of problems did you have with your Contis? I had the same tire before I bought a slightly used set of OEM 20" wheels and tires from another member here (finnfour). I was very impressed with the Contis but I did dish them out at around 25K miles which was pretty much almost the life I got out of them, I could have pushed them another 3K-5K miles but it would be cutting it close to being unsafe. I did however, see a faint line starting to appear in the middle of the tread that almost looked like if pushed more it would split the tire right in half.
On the first set, I got about 12 months on them (~30K miles) before I started to hear / feel a slight vibration that got progressively worse over time. I also started to get a vibration in my pedal and steering wheel when I was braking - which also got worse over time. On the first set, they brought me back to the shop and showed me one of the tires on the 'balancer' - it would pop up and over at one spot on the tire and said it was a 'belt shift'. At that point, I had already replaced 2 of the tires, so I decided to replace the remaining 2. After that, the problems went away. And then 9 months later, I started to get that same sensation again. I didn't wait as long this time around because it was exactly the same thing I had experienced before. But this time, they really couldn't find any reason for this to be happening. None of the tires looked bad and when they re-balanced them, they were always fine. But I would get that helicopter 'wop/wop' noise when driving on them.
I contacted Continental and they agreed to replace, what the tire dealer described as; the 2 tires they suspected were the cause of the problem, on a pro-rated basis. It didn't help. The tire dealer purposely kept the 2 tires that they took off in case it didn't resolve the issue, so I went back about 5 days later and had them swap the remaining 2 tires around with the new ones.....but I still had the issue. So, it looks like I have at least 2 tires that are bad again. I just don't have the time or the patience to keep going back to try a different combination of 2 tires.....I should have just insisted that they replace all 4. But, at the same time, I really don't want to buy a 3rd set (even if they are discounting them for me) and run into the exact same thing again a year from now.
So, I'm cutting my losses and buying the new set. I see on Tire Rack that there are a lot of people that have had similar experiences - they start out great, but then get noisy. But in my case, in addition to the noise, the vibration during braking is really annoying.....I thought I had really bad warped rotors when it first started happening. New tires made everything right again.
And since I do 98% highway driving, I was getting very good wear out of them. I replaced the 1st set at ~45K miles and I believe there was still about 6/32" left on the tires. With about 25K on the 2nd set, I think I still have between 7-8/32" left.
I hope I have better luck with the ENVigors.