I have a 4 year old Grace GMQ Pro frame that is essentially wood. It is in the basement (finished lower level) and there have been no problems. I have had to replace the tracks. Seems what Grace was using 4 years ago did not last. there is a Grace Machine Frame group on Yahoo and it has been discussed as how to buy and install metal that will make a quality, long lasting track. Shipping seems to be a problem for Grace, so they tend to use a flexible plastc that can be coiled, but in winter sub-zero weather, the track is cracked. I have a 3rd set of tracks on my frame.
June in Cincinnati