The researchers conducted a 50 - year life cycle cost analysis, assuming a 20 - year service life for white and black roofs and a 40 - year service life for green roofs. (newscenter.lbl.gov)
DS2 came out last year so if DS3 comes out next year, I think that a 2 year life cycle for souls games is perfectly fine. (n4g.com)
After the Lyme pathogen was identified, scientists in the Northeast traced the relatively simple two - year life cycle of the disease in nature, as depicted below. (discovermagazine.com)