Some of the DVD ram disks are made inside cassette type cases. For any type of storage media follow the guidelines on how to look after them. Disks should be stored vertically, away from heat, moisture, humidity, light, radiation (including any type of power device), away from dust, handled carefully without handling the actual centre piece of the disk, not thrown or dropped around, lol.

All these things will help to maintain the maximum life of the disk. DVD's are similar to CD's so ... if the commercial production house uses high or reasonably high quality media then they should last a long time. DVD's are too new on the scene to make verifiable judgements about but can be compared to CD's. I'm just glad there's not as many dvd media on the market & even cd production has improved .. though there's still 'el cheapos' out there better left alone.