In terms of arcade-style racing/driving games or casual racing/driving games, you don't want tracks to be brutally long, because most types can't take some very long courses. You want to be able to keep most players' interests in mind long enough and have easy enough courses to master. You also want to consider track length for mobile device games as well. Are you going to be content offering very long courses and some very long races if certain mobile devices can't handle it?
The lovely mobile racing game, "Assoluto Racing," was one of the first-ever mobile games (and maybe the only one) to offer the full-length Nürburgring Nordschleife. I have not tried the track out yet (when DO I want to try this track?), but having the full-length course in fine accuracy is an accomplishment. I have Circuit de la Sarthe in "Real Racing 3" for my two Android TV boxes. I wouldn't want to try pushing Circuit de la Sarthe on a smartphone or tablet. But... it's there if you're ready for it.
One more thing I thought about with track length is not necessarily about individual tracks. Think about open-world type racing games like the Test Drive Unlimited series. You have to wonder what races you set up in these locations and for how long. Using TDU2 as an example, you can have short races around a few miles/kilometers, or you could have the ultra-long races around Ibiza and Oahu/Hawaii- both time trials lasting at least 40 minutes covering hundreds of miles/kilometers.
Just a few extra things to think about in regards to track lengths.