I don't know how reliable this is, but I have used the numViews property for Portal items to get an idea of usage over time. I ran a script every day to capture daily view count, then use some other functions to see activity over time. Hope this helps!
from arcgis.gis import GIS
gis = GIS(portal_url, username, password)
# find all items
items = gis.content.search('', '', max_items=10000)
for item in items:
print(item.numViews)