The motor for my 95 3000gt antenna runs longer than it should when turning on and off the radio. It works fine but is a little annoying. The antenna will be fully extended but the motor runs for another 10 or so seconds. Any way to fix?

 

If you're up to the challenge of taking it all apart and tinkering with it... the answer is "YES", you can do it. You need to find the limit switches in connection with the plastic gear and set it accordingly to the desired length of your antenna. It could be tricky though and much dependent on particular design. I would suggest leaving it alone 'till it fails and then replacing it all along with the new stuff.
Permanent antenna would be my choice.