RUL. Based on official nomenclature. See the links:

Based upon Expected or Remaining Useful Life (EUL &
RUL) of building systems and equipment RUL) of building systems and equipmenthttp://www.engg.ksu.edu/chsr/outreach/tab/workshops/docs/8.B...


The Remaining Useful Life or "RUL" is a subjective estimate of the number of remaining years that an item, component, or system is estimated to be able to function in accordance with its intended purpose before warranting replacement. - See more at: http://www.partneresi.com/resources/remaining-useful-life.ph...

Building improvements to owned or leased buildings must be depreciated over the remaining useful life of the building or fifteen years, whichever is greater
http://apps.leg.wa.gov/wac/default.aspx?cite=388-835-0525


If the Remaining Useful Life of a particular Property system or component varies significantly (e.g., the Property consists of four separate buildings, and the roof is

The aim of the task is the planning and construction phases of the fire protection and maintenance rehabilitation for a remaining useful life of 8 years.



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Note added at 3 hrs (2013-12-31 15:47:40 GMT)
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The terms Useful Life (UL), Estimated Useful Life (EUL), and Remaining Useful Life (RUL) are commonly used in business. In the appraisal world, the term Useful Life is defined as the economic period during which a positive cash flow is expected for the improvements. For accountants and tax advisors, the term means the period to depreciate the asset.
http://criterium-commercial.com/how-long-will-it-last