560SL--Noisy fuel pump(s)

[cbdo]

Now that I've got a slightly leaky line at 17 years old and 164K), it's an opportunity to replace the fuel pumps. Since I bought it four years ago, they're distinctly audible with a mid-pitch buzz when running; it sounds mildly loud with ignition on/engine off, not overwhelming but clearly audible at idle, drowned out by normal driving in the city (25-35 mph).
Is this normal behavior for these, or loud enough to indicate significant wear and therefore candidates for replacement? I tend to favor the latter, remembering that this car was designed to impress people who were going to spend a lot of money to buy one.

[Gilly]

They'll get pretty noisy and still work OK. Is the plastic shield still there? Up to you, I know what you're saying about having the line/hose off it, but sheeesh these are expensive just to replace because they are noisy, you price out the pumps? Big bucks. Not too bad of a job to replace the pumps when you NEED to.
Gilly