I put Bosch duraterms in my 90 about 6 months before I sold it, maybe more than that. I can't remember. I sold it to a friend who drove it for a year, and then gave it back to me, and they were still all glowing strong. I put them in my 91 last year, and every one of them still works perfect. They are good plugs.
I know vwdieselparts.com sells Meyle I believe, and some of the forum members there have used them with good results.