Make you kind of wonder if 30-40 years from now, C&Vers will be finding old Carbon Fibre reinforced plastic frames and parts in the backs of sheds and rebuilding them, or will the plastic have broken down and worthless. Somehow I think the period from 2000 to 2025 will become known as the lost generation, since everything is plastic, digital and disposable and history will be left with nothing from this period.

The original Criterium RD on my PX10 lasted for ten years before one of the pulleys broke. It worked very well until then. I still have it and a NOS replacement for it.

I have two bikes set up with SX610s and one with a SLJ 6000. I don't think the shifting could be better.

The previous owner had replaced the pulley wheels with bullseye sealed bearing wheels on this one, and the whole thing works well enough. I'm just happy that it can handle a 30T cog...

Frank Berto is fond of saying that they should have named the Prestige the "No Prestige".

My experience reflects many of yours. The Prestige rear derailleur, out of the box, was probably the best performing of the boom era, European derailleurs. But they wore quickly and things got sloppy. I never liked the front derailleur. I also subscribe to the shifters being the weakest link. Very high effort was required to shift onto a cog of more than a couple teeth differential, due to the flex and high friction plate pressure that was required. Switching to metal shifters, Hyperglide cogs and teflon lined housing is a revelation in performance.

I always wondered how the early 1960s Prestige models without any metal reinforcement in the derailleurs or shifters performed? The single pulley Cadet must have been horrific.

As you proceeded up the line, you got lass Delrin and better performance and reliability. An SLJ model with retro-friction levers offered superb performance for the era.

In 1979, I bought a new PXN-10LE with a top of the line Simplex drivetrain. It was like butta!

Months later, someone stole the bike!

Oh, my first ten speed was an Atala Giro D'Italia. I got it new in 1975. It had Simplex prestige derailleurs, but the shifters didn't suck. They looked just like the shifters that came on PX-10's in that year but the metal wasn't finished nicely. I think there was a paper washer in there for some reason, and they needed readjustment and lubrication, but that was how all shifters were, and they didn't flex or break.

I did end up replacing the whole shifting system with a SunTour VGT Luxe rear, a SunTour Compe V front, and SunTour bar-end power ratchet shifters. That was a big improvement. I think that improvement plus tires were the only upgrades I did to the bike.

The SX610 has plastic arms covered by thin metal. I have a bunch of them and the only problem I've ever encountered with them is broken pulleys. There doesn't seem to be any play in the plastic arms. The SLJ6000 has similar geometry, but is all metal with an aluminum cage and pulley bolts. It's lighter and prettier, but I don't think it shifts any better than my SX610s. I use Retrofriction shifters on two of my Simplex-equipped bikes. The other has Criterium shifters because Retrofrictions won't fit. They're metal shifters, but they have the plastic wing nuts that always break. I keep some spares.

Did not have ay problems with the SX610s either when I had them on two Peugeots in the 80's
The design on the RD was not the "sexiest" and may look kinda clunky compared to a Suntour Cyclone MkII, but I think it's a more rugged design that can outlast the other good derailleurs of that time. Only plastic Simplex components I verntured into after the SX610s was their plastic retrofriction shifters in the middle of this pic of retro shifters in my stash:

Bought them more out of curiousity than anything else. Haven't tried it on my bikes yet cause they admittedly look quite clunky compared to the other Simplex later designed Mavic Retros next to it. I was thinking it might look good on my Vitus Carbone, but I can't seem to get over the clunkiness once I had them. I suspect they work OK with just maybe a hint of flex at the levers and they should last long as I never store my bikes exposed to the sun or harsh temperatures. But I do wonder why they even made these as they are not even the result of the carbon craze in the 80's and they do not have carbon stuff mixed into them as other makers did in the 80's (Modolo and Ofmega(?)). They were just Delrin.. Could it be to use up any stock of plastic materials/chemicals they had left over from the older days??
Chombi

My god! I can't believe that any of those things still exist based on my experience in the early 70's with my little white Peugeot! It didn't take long at all for mine to fail.

I just found a Prestige rear in my parts bin. I was surprised to find it. I don't remember how I got it.

I recently sold a Gitane that had barely been ridden. It was pretty much the same as a Peugeot UO8. All the Simplex stuff was intact, so I sold it that way.

Actually, I made one change: I took off the Mafacs and put on Weinmanns. I did that to increase my inventory of Mafacs.

I have a good collection of functional Prestige derailleurs and will agree that when they are new they shift beautifully... replacing the jockey wheels with Suntour is a good idea as these have a tendency to crack and break.

I used to replace Simplex pulleys with Bullseye, but the price of those went through the roof.

I have a 1971/72 LeJeune that came with Prestige(not Criterium) derailleurs on it. When it came into my possession, the RD had been replaced with a Suntour. Could somebody point out the right model of Prestige I need to keep around in case I want to go back to original.

The FD has a crack that goes about halfway through. It took a while but I scored a Simplex all metal(not Prestige) replacement.