Lots of people have a house rule prohibiting sending anyone making over $100,000 to the minors. Personally, I don't have that kind of self discipline.
I just had a guy I'd gotten in trade when he was 34 ... HoF-bound, but at the time I got him, he'd only been on 1 All Star team. In the three years he was my starting SS, he went to the AS game every year, hit .359, .349, and was hitting over .350 (ratings 5-4-4) in July when I reluctantly resigned him to $2.77M, 1-year after he set the FBL record for hitting streak at 41 games. By the end of last year he had over 2600 career hits. I had to bench him in August, after a 3-50 run. He finished the year at .332. He's had 8 AB in 8 games this year for .125, and is making his $2.77M hitting .235 in AA.
Three AS years in a row followed by .235 in AA ... yeah, they tend to slip fast....
Here's a screenie of his Career Stats page ...