Liquid lubricants and greases used in space applications are generally susceptible to degradation or aging. Depending on the specific material combination and storage conditions, aging effects are also relevant for long-term storage (LTS). An overview on both physical and chemical aging processes for liquid lubricants and greases is given and processes which are seen as relevant for LTS and may impact the long-term performance of these materials are identified. Individual degradation processes as well as causes and potential risks are discussed, providing complementary data for two liquid perfluoropolyether (PFPE) lubricants (Fomblin Z25 and Brayco 815Z) and a PFPE grease (MAPLUB PF 100-b), focussing on thermo-oxidative and catalytic degradation. For these lubricants, monitoring of degradation effects is done indirectly by their mass loss at different temperatures and in the presence of a catalyst over a total duration of 1000 h. An increased mass loss during accelerated thermo-oxidative aging at temperatures above 200 °C is observed, with overlapping effects of thickener degradation for the investigated grease. Noticeable catalytic degradation effects are further seen for accelerated thermo-oxidative aging in the presence of Al2O3 above 200 °C.