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ESA's XMM-Newton space observatory launched in 1999, is the flagship of European Xray astronomy and the most powerful X-ray telescope ever placed in orbit. The mission, originally designed for a 10 years lifetime, is planned to be operated long into this decade since spacecraft and instruments are performing admirably without major degradation. The ultimate mission end of life was defined as 2019, limited by the hydrazine reserves on board. Since scientific demand on XMM-Newton is very high and the mission has been ranked top level by the ESA advisory structure, various options to reduce the fuel consumption have been investigated. Some of these have been put in place in the course of the last years, especially we have updated the on-board software of the Attitude Control Computer to allow operating all four reaction wheels in parallel instead of only running three of them as done previously. Simulations and experience from ESA's HERSCHEL mission have shown that this should reduce the fuel consumption by up to a factor of two. In addition, operating with four reaction wheels offers the possibility to apply some measures against increased bearing noise due to aging, which has been detected on two of the XMM-Newton reaction wheels. The usage of all fuel saving methods may extend the potential lifetime to 2030. We present the implementation and results of the applied fuel saving methods and describe the increased bearing noise and its mitigation measures. In addition will report on the outcome of relubrication exercises performed on two of the wheels to cure the increased bearing noise. Furthermore we describe plans that are currently developed to operate the Hydrazine Propulsion System in the so-called near fuel depletion regime at the end of the technical life limit. In addition, ground segment evolution related to hardware, software and automation possibilities facing the new very long term perspective are discribed.

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In early 2015, ESA's high energy astronomical observatory INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) performed a series of manoeuvres to enable the disposal of INTEGRAL via an uncontrolled re-entry into the Earth's atmosphere in 2029. These manoeuvres used approximately half of INTEGRAL's remaining fuel. At the current rate of consumption, fuel would be exhausted by early 2020 already and thus probably be the satellite's lifetime limiting element. Following these manoeuvres, different ways to reduce propellant usage were investigated.This paper summarises the general concepts of various fuel saving options. Indications suggest that it is possible to achieve major propellant savings in the coming years at very low implementation costs. This could allow ESA to extend INTEGRAL's science operations phase considerably and thus provide the high energy astronomical community with a solid observatory well into the next decade. Furthermore, it could possibly even allow for a controlled re-entry in 2029 with some residual propellant available for a trim manoeuvre in the mid to late 2020ies. Such a manoeuvre would enable ESA to fine-tune the re-entry longitude, position and profile.