City Care were contracted to maintain the tree and have been implementing an ongoing watering and fertilising programme.
A report from February 2014 determined the tree had stalled the ongoing decline and showed an increase in its vigour and vitality.
In May this year, 15 months since the last inspection, another was carried out.
Mr Aitchison said the later timing of this assessment meant the tree was in an advanced stage of autumnal leaf fall.
He said there had been no fruiting bodies of honey fungus found on the tree, which had been noticed in two different spots in previous assessments.
"Although with the later timing of the inspection these may have been and gone."
There were "healthy signs that the tree is maintaining its overall vigour in response to the stresses that it has been subject to," he said.
"There is no significant dieback apparent in the canopy."
Mr Aitchison said the structural integrity of the tree appeared to remain intact, and the decay site noted in previous reports at the base of the trunk did not appear to have increased in size.
"The assessment shows that this tree is maintaining its health status and slightly improving as regenerating inner canopy growth continues to develop."
Farley family descendant and Greytown Community Board member Ian Farley said the tree had "improved immensely over the last three to four years" as a result of City Care's work.
SWDC amenities manager Helen McNaught said City Care staff had been taking good care of Farley's Oak.
They had been following the arborist's recommendations, which included making sure it was well-watered over summer.
"The tree's health is slowly but steadily improving, which is a delight to see."
Mr Aitchison advised council to continue with the watering and fertilising programmes.
