而在美國國家技術標準協會(NIST：National Institute of Standards and Technology)
所做的研究Care and Handling of CDs and DVDs http://www.clir.org/pubs/reports/pub121/sec1.html
(文章在美國圖書資訊研究會Coucil On Library and Infomation Resources)
的第4節
4. How Long Can You Store CDs and DVDs and Use Them Again?
的第3項 http://www.clir.org/pubs/reports/pub121/sec4.html
4.3 CD-RW, DVD-RW, DVD+RW, DVD-RAM Discs
RW and RAM discs are generally not considered for long-term or archival use,
and life expectancy tests are seldom done for this medium. Rewritable discs use a phase-changing metal alloy film for recording data and aluminum for the reflective layer. The alloy film is not as stable as the dye used in R discs because the material normally degrades at a faster rate...
(RW&RAM的金屬層(資料儲存在這裡)不如染料(DVD+/-R的記錄層)穩定，因為材料品質降低的速度較快)
The phase-changing film is affected primarily by heat, but ultraviolet (UV) light may also be a factor in the aging process. The combination of high temperature and UV light may further accelerate the aging process.
The combination of high temperatures and high relative humidity will also most likely accelerate the aging process, just as it does with the organic dye used in R discs.
(和 DVD+/-R 一樣，高溫&濕度、紫外光也會加速老化) <==很多人都認為相變化材質不怕光照，這是否定的
The data on the phase-changing metal alloy film layer can be erased and rewritten to a limited number of times (about 1,000 times for RW discs and about 100,000 times for RAM discs).
This rewriting does, however, affect disc life expectancy; RW or RAM discs archived after the first recording
should have a longer life expectancy than those that have undergone several erase-recording cycles.
Given the normal degradation rate alone, the life expectancy for RW and RAM discs will be less than that of R discs.
Add to that multiple rewrites, and the life expectancy can be even less.
(多次寫入會影響壽命，寫一次比重複寫入幾次後的預期壽命高。
依照正常的速度，DVD+/-RW與DVD-RAM的預期壽命較DVD+/-R低，多次寫入後，預期壽命比DVD+/-R更低)
現在看到這篇真不知道哪個才是正確了
