Robert M. Gary writes:

I know that the AIM tell us that class E airspace traffic advisories
are given to VFR aircraft on a workload basis. However, I seem to
recall some of our controller friends saying that as long as an
aircraft is currently being given flight following the controller must
either advise traffic or cancel the flight following. I'm looking for
this type of language in the 7110 but I'm not seeing it.

The controller is not required to call out all traffic, and may not be able
to. The pilot should always assume that there may be traffic nearby that the
controller cannot point out. This is mentioned in the pilot/controller
glossary of the 7710 under Traffic Advisories:

"Traffic advisory service will be provided to the extent possible depending on
higher priority duties of the controller or other limitations; e.g., radar
limitations, volume of traffic, frequency congestion, or controller workload.
Radar/ nonradar traffic advisories do not relieve the pilot of his/her
responsibility to see and avoid other aircraft. Pilots are cautioned that
there are many times when the controller is not able to give traffic
advisories concerning all traffic in the aircraft's proximity; in other words,
when a pilot requests or is receiving traffic advisories, he/she should not
assume that all traffic will be issued."