These relay contacts are not copper. They're some sort of Nickel, Silver, or Indium alloy to withstand the high current and arcing that happens with DC circuits. Like breaker points, they're a solid slug of metal, not a plated contact like most ice cube relays. They can stand a decent scrub when they get rough like mine and helps them to last longer. Eventually they'll get to the point that the relay has to be replaced, I'm just getting more time out of it before its time is up.

Regarding the boost problem....10-12PSI is stock for the 617's, 12-14 for the 603's. If you're running the ALDA, it would be worth your time to pull it and replace the 2 O-rings in it (test if the ALDA holds vacuum with a mity-vac. It should hold strong vacuum indefinitely). If it's never been done before, they're toast (probably like hard plastic) and it has a dramatic impact on how soon and how smoothly the boost comes on. Before replacing the ones in my car, boost wouldn't really build until >2100 RPM, then came on all at once. Really fun to drive in the rain! NOT! After replacing the O-rings, boost starts building meaningful amounts ~1700-1800 RPM and comes on smoothly. When driving normally, you don't even feel it come on. You'll notice from a floored standing start, but it's not the rough kick in the rear that it was before.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]