My serger, too, is almost 30 years old. I love it, but sometimes it jumps, makes a clicking noise, and the right needle thread is caught in the seam where it is not supposed to be. This happens most on thick seams. I guess it is out of time, and my fix-it guy can't seem to get it right. I don't know if I would get rid of this one, but I would like one that does the cover stitch.
A lot of people have two sergers, one with light thread and one with dark.