Employing Channel Probing to Derive End-of-Life Service Margins for Optical Spectrum Services. To appear in OPTICA Journal of Optical Communications and Networking. - Kaida Kaeval; Frank Slyne; Sebastian Troia; Eoin Kenny; Klaus Große; Helmut Griesser; Daniel C. Kilper; Marco Ruffini; Jose-Juan Pedreno-Manresa; Sai Kireet Patri; Gert Jervan (CoRR, 2023)