The recent launch of the Landsat-8 satellite, in parallel to the opening of 40 years of archives issued from the Landsat program, has created new opportunities for the design of large-scale initiatives for environmental monitoring at moderate spatial resolution. However, the availability of cloud-free observations stays a major limiting factor, especially in wet tropical areas like South East Asia (SEA). Based on the analysis of one year of Landsat-8 data acquired for the 69 path/row combinations that intersect SEA with the Fmask algorithm, we studied the temporal granularity of cloud-free observations. Our results show that the annual production of two quasi-complete composited maps for SEA seems achievable when 'greenness' and 'brownness' are close to their maximum, offering relevant opportunities for scientists and stakeholders involved in environment, biodiversity or health issues.