Infiltration as a fabrication method for solid oxide fuel cells (SOFC) electrodes is offering significant improvements in cell performance at reduced materials and fabrication costs, especially when combined with co-sintering. However, important questions regarding the long-term performance and microstructural stability remain unanswered. Here, we present the results of a three-year project, where large footprint anode-supported SOFCs with a co-sintered cathode backbone and infiltrated La0.95Co0.4Ni0.6O3 (LCN) cathodes were developed and thoroughly characterized. The initial long-term performance and stability of this new cell type was investigated for 1500+ hours, coupled with STEM-EDS investigation of the microstructural changes in the infiltrated electrodes. Additionally, electrodes were further aged at elevated temperatures (750 - 900 degrees C) for periods reaching up to 5000 hours, while following changes in the electrode properties using SEM, BET area, and in-plane conductivity measurements. Finally, the mechanical properties of co-sintered cathode backbone cells were determined in four-point bending tests carried out both at room temperature and at 800 degrees C in air. Based on these results, degradation mechanisms were identified and recommendation for safe operation conditions in real life application could be formulated. (C) 2017 The Electrochemical Society. All rights reserved.