When to CLA a Lens?

I recently had all of my Canon SLRs CLAd by Ken Oikawa. I've read in some user's posts that they also send their lenses in. I'm curious if Canon FD and FDn lenses "fail" like the cameras do. Is it recommended and common practice to send your lenses in to a tech or are lenses pretty much good as long as you don't notice any issues?

Thanks

~Brad

I don't know about Canon lenses but with Nikon manual focus lenses my experience is that the grease in the focus mechanism goes out every decade or so. When the focus gets too loose for comfort I send them for professional overhaul... and have never had a lens related failure.

No, lenses if they work ok are best left alone I've been shooting with Canon New type (plastic barrel) lenses all bought second hand over the last forty years and they all continue to work perfectly without ever been served.

If there is nothing wrong with it I'd leave it alone.
I regularly service Zeiss Jena and Meyer Görlitz lenses and some of them are perfectly useable, even after 60 years of gathering dust in a closet.
It is only when the aperture blades stick or the focus gets stiff you might want to have it serviced.
Apart from that: Never touch a running system or so.

If one is shooting in extreme conditions such as cold weather, excessive heat, dust, ... the lenses should be CLAed. Also it the lens has sat for a long time without being used the lens should be CLAed.

I would go by practical experience with any particular optic. if the diaphagms becomes sluggish, focussing becomes sloppy, stiff or 'gritty', if there is more than a tiny amount of dust inside on internal optics or the apperture ring becomes loose or tight, are a few pointers. Other than that they are pretty reliable. Other than that I would leave them alone.

I have only had 3 lenses looked at in half a century of photography. One was an Olympus 21mm F3.5 where the rear element was badly scratched and that was replaced (I bought it for next to nothing) a Nikon F2.8 35mm whiuch I had converted to the Ai specification and a Rodagon 50mm 2.8 apo enlarging lens when the apperture ring siezed up.

Anytime. A good product can be disassembled and assembled many times without taking damage.
A Taylor Hobson Trital I have opened must have been warm one time in the past, the grease has flown out and spread over parts where it’s not needed. Chemical reaction of the sulphur contained in the mineral grease with the copper of the bronze alloy turned it into the well known blue-greenish sticky mass. With a Pan-Cinor Berthiot that has anodized aluminum parts the old grease was more or less okay but made an almost air-tight bond on the moving tube so that zooming was a drag. There was too much lubricant anyway. They lubed lenses for lifetime sixty years ago, grease is cheap.

With mass produced lenses not all glass rims are blackened, a good opportunity to paint such is when the lens doctor puts his operation gloves on. New set screws are a good idea, too. Looks well. Lenses with plastic parts I abhor.