They won't give you ultimate racing grip after a few years, but they will still have so much more traction than DOTs in the rain even after 7 to 8 years. It also depends on how often you run them and if you run them in the drying conditions and overheat or wear them down of course. Mine had not seen much use.
I had a blast passing everyone on track except one coach who also had rains on my 8 year old rain tires. I am not a fast guy, but the guys on the DOTs (or slicks) didn't stand a chance. With that said my rains are 10 years old and starting to crack a bit, I have finally decided I am done running rains. It was fun, but just is not worth the hassle for me. If your bike already has a quick change set up on it, maybe it wouldn't be so bad, but I generally lost a session putting the rains off and another taking them off. So most of the time I did a bunch of wrenching for one extra session. The exception was the day I mentioned above where it rained all day and eventually the puddles got too deep even for my rains toward the end of the day. I am converting my rain wheels to a set of slicks ready to swap on, well at least the rear.