Magneto calendar overhauls - the thin end of the wedge?

[Perspective]

I hear ya,
Interesting, not the first time I've heard contradictory information,
Maybe get that in writing, I know I'm going to.
So here we are, I've spoken to my Surveyor and the information is that the SB is created to inform of the
TBO and Inspection periods for the Component.

So I hear you, that because it doesn't say Mandatory Service Bulletin, its optional, Ok then, no probs,
lets look at the Bendix Overhaul Manual, which is part of the approved Data which is consistently referred to on numerous
occasions. As I think most people are now comfortable that the Sched 5 is a list of things to look at, and the Maintenance and Component
overhaul Manual is the Approved Data, what does the approved Data say,
Bendix Manual.
2. "General Overhaul," as specified in Section 7-2, must be performed at the same interval as engine overhaul, or in the event of severe environmental effects
(engine overspeeds, sudden stoppage or other unusual circumstances), or at the expiration of four years without regard
to accumulated engine operating hours since new or last overhaul.

This is from the approved Data, The SB Highlights what's in the Manual.
However you look at it, whether you refer to the SB or Component Manual, the requirements are the same.
Your LAME Would have had it drummed into him no Doubt that he must have the latest revision Data for the Aircraft he is Working on.
Within That are references to the Components and relevant component Manuals.
He may have also read in the Piper manual, where they point out the use of SB's and MSB's, where Piper consider all to be Mandatory!
Some Background info,



from Aviation Occurrence Investigation 200600001, section 1.18.5,
As well as
4.2.2 Airworthiness bulletins and advisories
Safety issue
Currently, Civil Aviation Advisory Publication (CAAP) 42B-1(0) and
Airworthiness Bulletin AWB 02-003 Issue 2, are ambiguous regarding required
inspection intervals for Private category aircraft airframe items. This may result in
the items being operated past the specified aircraft manufacturer’s inspection
interval.
When you look at the Common Law, outlining the application of Schedule 5,

2.6 In this Part:
general maintenance inspection means a regular inspection
and check of a class B aircraft, its systems and components
that:
(a) is required by the aircraft’s maintenance schedule to be
carried out at regular intervals;

The TCM Service bulletin is what's used to outline the TBO Period for the component, in this case a Bendix Mag,
Remember that,
The CASA maintenance schedule, which is Schedule 5 of the CARs, is
widely misunderstood. Many think it replaces and relaxes the manufacturer’s
maintenance schedule.

When using Schedule 5,
6. Periodic Inspection Schedule

6.1 The replacement or overhaul of time-lifed components required in an Airworthiness Limitations Section of the aeroplane’s maintenance manual and any special techniques required by the manufacturer or an Airworthiness
Directive are required to be complied with.

CAR 1988
(f) set out details of the approved maintenance data used to
carry out the maintenance;

I wait to see what I get back from Southern region, But I think I know the answer and am happy to PM you
the results.