I'm changing my answer. π
I'm 21 sea days from diamond. We've quit going to the platinum party and I don't know that we'd make an effort to attend every diamond party. Might be that the diamond parties are much nicer and if that's the case I'm sure it's something we both look forward to attending.
On the flip side, I can see cutting back on these benefits on the short and cheap cruises. This is what I mean when I say I don't cruise for the benefits, though I sure like some of them. The laundry comes to mind. It seems the ONLY additional benefit of any meaning for diamonds, other than the initial benefits of a free dinner and upgrade, would be the nicer cocktail party. I don't drink, but if the party is a step up, that's something I'd learn to appreciate pretty quickly.