Hi!
I would recommend to avoid doing it all the time on lateral clutch chronograph movements (like your Breguet type XX) because of the added wear between the parts. However, if you don't mind servicing your watch maybe a little more often (every 4 year or so), it really shouldn't be a problem.

A vertical clutch chronograph induces no additional wear and can be activated permanently and it makes no difference on the movement.

 

I don't keep my chrono running, but I agree that some movements can do this with no issue.

 

I think the more important question is, why would one want to do this?

 

Heck no. Don’t do this.

 

I don’t see the point. If one does not like seeing a static second hand, the more practical and effective solution would be to get a simple 3-handed auto.

I can only imagine that a continuous running chrono just adds unnecessary wear.

 

Like you, I used to do this as well, but later realized it drained the power reserve. Also, as others mentioned, it does put unnecessary stress on the movement.

 

Like you, I used to do this as well, but later realized it drained the power reserve. Also, as others mentioned, it does put unnecessary stress on the movement.

The power reserve is how much energy is in the spring; increasing the load doesn't change that. However, when the reserve is low, the watch will stop sooner if the horizontal clutch is engaged at that time. Disengaging the clutch at that time will lessen the load and the watch will start running.

 

On a lateral (horizontal) clutch, typically only one small gear wears a bit sooner. On a Speedmaster, it's about $25 according to a post by Archer. On a vertical clutch, there's no wear and tear but, without occasionally disengaging it, it can seize and never disengage (on some movements like the Seiko 6138/6139 and the early Citizens).

The bottom line, ask the manufacturer

 

On a lateral (horizontal) clutch, typically only one small gear wears a bit sooner. On a Speedmaster, it's about $25 according to a post by Archer. On a vertical clutch, there's no wear and tear but, without occasionally disengaging it, it can seize and never disengage (on some movements like the Seiko 6138/6139 and the early Citizens).

The bottom line, ask the manufacturer

I think the main problem is not so much the part that gets worn, it is the microscopic « débris » (sorry I don't know the term in English) from the wear that will end up in other places of the movement, between other parts and gears and will accumulate over time all over the movement. But it's not significant enough to damage anything unless you never service your movement. Increasing the frequency of service was what Omega told me to do if I wanted to do that (and the construction of the movement on my moon watch is similar to the Bréguet type XX).

 

I have a Breguet Type XX as well and limited to my own experiences, it doesn't seem to matter whether I keep the chrono running or not vis a vis longevity. For one reason or another, something goes awry and I have had to service my Type XX every 3 years. It's as if the watch knows that its about to hit the 3 year mark since its last service.

That said, my Type XX performs at +3 seconds per day with the chrono off and at -23 seconds per day with the chrono on, so I tend to keep the chrono off as it keeps better time that way.

 

That said, my Type XX performs at +3 seconds per day with the chrono off and at -23 seconds per day with the chrono on, so I tend to keep the chrono off as it keeps better time that way.

If you didn't know, that shouldn't be. The added load of the chrono shouldn't impact the rate except, perhaps, when the mainspring is low.

 

I meant to write that the extra load from the chrono shouldn't impact the rate that much except when the mainspring is low.

 

I have so many chronographs I barely use the Chrono function. I guess it's more of an aesthetics thing.
To me, most chronographs that are tastefully done look great.