I've repeatedly considered hiring someone to write new material for me, but being the micro-manager I am, I know this just wouldn't work.
Why? Because it can be soooooo frustrating to come up with new material (especially if we feel it's particularly witty or clever) only to receive dozens of messages from people who didn't bother to read ANY of it. They look at the photos and rates, that's it.
Hell, I've had guys who've claimed not to have even seen my photos! They allegedly decided to see me based on my reviews and profile alone. So naturally, they have no idea where I am when they're making their request, let alone any other pertinent details.
Personally, I don't believe they didn't at least click one of the links to see my pics..... they just ignored everything else.
This sort of thing really makes me feel like trying to keep my site & ads "fresh" by changing/updating my dialog is largely pointless.
Clients who truly want to learn more about ME (not just what I offer) prior to meeting will often read my blogs, follow me on Twitter, or search my posts.
So nowadays, depending on which ad site or venue, I just keep the ad text the same (only updating necessary details) or pare it down to the basics.