My 4506 i bought new in 1990, sent it to Robar for NP3 carried it for 10 years or so then went the plastic route and recently just switched back to my 4506. After a complete re-spring job, a new trigger since original had some hairline cracks, and 5 new mags, XS Big Dot sights. planning on carrying until i retire.
Stainless has held up very well especially with the Robar NP3 finish.
Just added a CS-45 that just arrived from Birdsongs with the Green-T Finish.