This is more of a question for the GA guys.

In the pilot's operating handbook of any S-Tec autopilot (let's say the System 30 in my case), they outline a preflight check to perform with the engine running before takeoff. These checks include mode checks, disconnect checks, override checks, etc. which are common to all autopilots.

Flying Lears (or any jet for that matter) we obviously do similar checks on the autopilot at least on the first flight of the day. However, I am training someone for their instrument now on a C-172 with an S-tec autopilot. While performing the checks as outlined in the manual, I sometimes fear we're being rough on the system (even though we try to be gentle!), such as during override checks (i.e. holding pitch up/down until you get a trim up/down light). As an example, when we test the disconnect, even though we've neutralized the yoke (no stress) a "thunk" can sometimes be heard from the servo in the tail.

My question is, although the manual calls for it and it's good operating procedure..... from a practical/mechanical standpoint in terms of the system, is it still a good idea to do these checks? Although it's obvious for the bigger jets (can't get around SOPs), does the same hold for a light piston with a basic autopilot system?

Thanks