Due Diligence While Buying a Used Camera

[Thad E Ginathom]

Sorry, Krish. I got the identities of who was saying what mixed up there.

Not really trying to prove anything. I was taken aback at the suggestion of people doing regular services. Did a very small bit of asking around.

Yes indeed, only anecdotal.

[Krish Chandran]

Cameras are not cars which require oil or filter change.

Response to the question "do you take your camera for preventative maintenance" is almost entirely no. One person said, that belongs to some cameras for adjustment of shutter speed and lubrication.

Krish, do you?

Or is this whole thing another unjustified speculation ;)

I did not read any response saying anything either way. ,Where did you read that ? 

Somnath suggested reading service history at authorized centers may be a good source of cross checking the stated condition
My point was that the records themselves may not present an accurate picture, whether that is due to either people not taking cameras for repair/maintenance or not taking them to authorized centers for repairs - where these records are maintained. No one knows accurately. 
Your personal anecdotal experience suggests "no one takes their camera for preventive maintenance" Something you seem determined to establish. 

Okay, maybe you're right. Now what? The OP still wants to know how to check and what to check while buying used cameras. What advice do you have for him?  
 

[Thad E Ginathom]

Cameras are not cars which require oil or filter change.

Response to the question "do you take your camera for preventative maintenance" is almost entirely no. One person said, that belongs to some cameras for adjustment of shutter speed and lubrication.

Krish, do you?

Or is this whole thing another unjustified speculation ;)

[Krish Chandran]

I've heard many cameras develop new issues after unnecessary services the official service centres. Cameras are not cars which require oil or filter change.

Interesting. Are there any verified reports or published examples of this happening, or is it mostly based on forum rumors? It would be good to know if any specific brands or centers have been documented doing this, or if it's just unverified speculation? 

[Monster]

Yes, I live with a minor bug in my Sony A7iv: sometimes it gives two clicks for one shutter push. And it's out of warranty now so I probably will never do anything about it.

But, without an actual fault that seriously affects usage, I have no plans to take my camera(s) for "maintenance." In fact, unless it has to be taken apart, I'd rather every screw remained in in its factory-set state.

We are hobbyists here. I don't think there are going to many maintenance trips: does anyone here actually do that? Not what good reasons might there be, but does anyone?

I've heard many cameras develop new issues after unnecessary services the official service centres. Cameras are not cars which require oil or filter change.

[Thad E Ginathom]

Yes, I live with a minor bug in my Sony A7iv: sometimes it gives two clicks for one shutter push. And it's out of warranty now so I probably will never do anything about it.

But, without an actual fault that seriously affects usage, I have no plans to take my camera(s) for "maintenance." In fact, unless it has to be taken apart, I'd rather every screw remained in in its factory-set state.

We are hobbyists here. I don't think there are going to many maintenance trips: does anyone here actually do that? Not what good reasons might there be, but does anyone?

[Somnath Goswami]

A machine with zero logged issues might look perfect on paper, but it usually just means it hasn't seen a professional technician in years.

How often does the average camera need professional maintenance? I have never once heard of anyone taking their camera for such a thing, except for those who are scared to clean their own sensor.

Maybe really heavy users such as professional sports cameramen?

Or gear that see less use. For instance nikon 500 and 600 f4 primes suffer dead motors if they are lying unused for prolonged periods.

[Krish Chandran]

A machine with zero logged issues might look perfect on paper, but it usually just means it hasn't seen a professional technician in years.

How often does the average camera need professional maintenance? I have never once heard of anyone taking their camera for such a thing, except for those who are scared to clean their own sensor.

Maybe really heavy users such as professional sports cameramen?

Personal anecdotes and service records only show what gets reported, not the actual health of cameras out in the wild.
Relying on that data to judge reliability leaves a few blind spots:

• Plenty of users live with minor bugs, slightly misaligned autofocus, or sticky dials without ever sending the camera in. Zero service history usually just means the owner found a workaround.
• Invisible maintenance: A lot of gear is fixed via third-party local shops after warranty ends simply because it is the cheaper option
• Pro vs. Hobby Users:  You're right about heavy users. Sports shooters, wedding pros, and rental houses (especially them)  heavily use their gear and run it through regular maintenance cycles that the average hobbyist never even thinks about.
  
   At the end of the day, service logs track repair behavior, not how many cameras are actually running perfectly behind the scenes.
  
  
  Edit: When they  come on to the second hand market both heavily used "pro" equipment and lightly used "hobby" equipment swim in the same pool. That poses a bit of a challenge for the prospective buyer

[Thad E Ginathom]

A machine with zero logged issues might look perfect on paper, but it usually just means it hasn't seen a professional technician in years.

How often does the average camera need professional maintenance? I have never once heard of anyone taking their camera for such a thing, except for those who are scared to clean their own sensor.

Maybe really heavy users such as professional sports cameramen?

[Somnath Goswami]

Always important to remember what Carl Sagan said : absence of evidence is not evidence of absence.