hi i have a 91 and its bullett prof as with any machine you have to keep up with the servise i do my own work and i check the sync every 20000miles only once i had to make a small ajustment like any thing if you get your hands on a well looked after bike it will out last your rideing days
90 K is just broke in. 90-96 were almost all the same, part wise, very few changes during those years, and basically trouble free machines. They did make a few minor changes for the 97 model and above, but a couple of quality control items surfaced during the newer models also, such as the cheaper built alternators on the 97+ models, and some fit and finish problems. But a couple of improvements were made also such as a lower seat, and an improved shift fork. The nice thing about all of the 1500s is that there is probably more interchangeability of parts across all model years than any version of the Goldwing. Plus, there is more aftermarket parts for a 1500 than for almost any other bike. Overall, the best Honda ever built, and although I now own an 1800, I know the 1500 is a bike that if taken care of can easlily last 300-400k.
One thing to watch for is the LCD screen that shows radio and suspension settings, (situated between Speedo and revcounter). If there's a half moon shape (black) appearing at either side it will get worse until you can't read the info. They are very expensive- even 2nd hand. Mine was like this, and the previous owner knocked some off the price because of it. I thought I'd get one off ebay for a few quid- Wrong! They're over £700 new in the UK (a bit less in the States) and 2nd hand prices reflect this. I eventually paid about 300 dollars (with delivery) for one off an '89 model. Early models seem generally less affected by this. It's a pig to change too. I love the bike though...Steve