Are you referring to shark fittings? I like them and use them myself. I've wondered about the life span of the o-rings but I haven't had any fail yet and some are about 6 years old. I've had soldered joints fail in the past so they're not guaranteed. I also use Pex now instead of copper. Where I attach Pex to copper I use a shark fitting.
I put in a water heater a few weeks ago. $540 for a 50 gallon gas heater from Home Depot and a couple of hours work. Didn't use shark fittings or pex because the old heater had flexible copper connectors. Worst part was getting the old heater up the stairs from the basement, god, those things get heavy after being in use for 10 yrs.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13