I'd tend to agree. It won't harm you to go over, but since no one's going to see it, what's the point, generally. Now, if you feel thinks are being cut off arbitrarily (like the name of a product) and those keywords should be included somehow, fine - go over the limit. You can potentially rank for those terms and they may show up in other places. Some directories, social networks, etc. read the title tags, too.
If it's just ego, though, like a long brand name, I'd suggest letting it go. Unless you're a really big brand, it's not going to matter that much, and you're likely to rank for your brand anyway. If the brand is getting cut off, then name recognition won't help your CTR anyway.
Usability research definitely shows that people pay much more attention to the front of a headline, and even just the first two words, so even if a longer title "makes sense", people may not care or even see it. So, sometimes, I think we obsess over getting something just right that may not end up mattering that much, practically.
Personally, I'd pick a different battle with the client, and maybe just keep a few long that are critically important.