Three years, for those above the Foundation Establishment Stage, is not considered a lengthy period; one could be in closed-door cultivation for a moment, and upon emerging, find that three years have passed.
After the war ended, the Longevity Sect basically entered a phase of re-development in the Eastern Region.
Therefore, these three years were uneventful, with the only significant changes perhaps being the architectural style of some newly rebuilt buildings and the expansion of a large market area at the foot of the mountain.
Chen Dengming had left an incarnation behind to preside over the sect; under the assistance of Nascent Soul elders like Guan Chao, it dealt with various affairs.
The Incarnation possessed his wisdom and logical thinking, and could share information at any time through the Soul Imprint, thus Chen Dengming was thoroughly aware of every minor and major development within the sect.