Future high performance Earth Observation satellites in Low Earth Orbit (LEO) will be equipped with high rate telemetry architectures either based on X-Band (375MHz, from 8.025 GHz up to 8.4 GHz) in dual-polarization or on K-Band (25.5GHz up to 27 GHz); in particular, the migration to the K-Band is expected in case the available X-Band will not be able to sustain the mission requirements. They will be also characterized by the on-board availability of a set of coding and modulation schemes at several spectral efficiencies and different Signal-to-Noise Ratio (SNR) thresholds; these will enable the usage of Variable Coding Modulation (VCM) techniques to improve the system performance by adapting case-by-case the coding/modulation scheme to the actual local atmospheric conditions. Among the requirements that a communication system engineer shall consider in the design of the telemetry architecture, the link availability is usually not considered as a critical parameter: for X-Band is it a common approach to size the system at 99.5% of link availability at the end of coverage area i.e. at 5° of elevation angle of the ground station antenna. This paper will show that for future K-Band transmission the target link availability need to be carefully evaluated in dependence of the required data timeliness: as a general rule, a trade-off among data timeliness and overall data throughput is expected to be necessary before sizing the communication architecture.