Is there any merit in trading up every couple of years or??
This depends on your situation. If you're trading a Stingray for a Stingray, then I would say it's not worth it. Keep yours and enjoy it. Upgrading to a Grand Sport or Z06 - well, this will depend completely on whether or not you're willing to have the extra expense of taking a loss on your current vehicle and spending more for what is essentially the same, but with a bigger body and potentially more power (and the badge, of course).
Interested to know what kind of kms your car has?
I have a 2009 Base 1LT that I got in July of 2019. It had 59k km on it. Now, it has 72k km on it. I bought this car specifically to drive it, and I have been very much, as you can see.
My situation is different from yours as C6 Corvettes have basically stopped deprciating. I can continue to drive like this and will lose minimal value when it comes time to upgrade.
What is the feeling about your car and mileage and when do most plan on trading up?
I feel with trade-ins, if you want the vehicle to maintain value from having low km, you need REALY low km. We're talking under 2k/year or less. Basically a collector car/garage baby. If you ACTUALLY want to drive it, then the mileages that I feel have an effect on value are 60,000 km and 100,000 km. In my personal opinion (not professional) a Corvette that has hit 100,00 km is no longer desirable at all because it's clearly been driven a lot.
My $0.02