From a product perspective, we tend to need to set guidelines that can be quantified, but I'm afraid the whole truth is never quite that black-and-white. All else being equal, I think keeping your titles to a reasonable length is beneficial. Long titles don't automatically harm you (there's no Capital-P penalty for it), but they tend to create a few problems:
(1) Often, long, CMS-generated titles front-load repetitive words (like the site name or category/sub-category), which devalues the unique/important words in Google's eyes and is more likely to make it look like duplicate content.
(2) Long titles tend to devalue important words for search visitors as well, which can harm click-through rates. I'm a firm believer that CTR has indirect impact on ranking over time. Even if it had no SEO significance, it's generally bad for engagement and for your site.
That said, it depends a lot on what you're dealing with. If a title of a page is, say, a title of a blog post, and it's just a long title, that's probably fine. If you have 5,000 product pages that all start with "Bob's Discount Propane Warehouse | Propane and Propane Accessories | ...", then that's going to be detrimental to your usability and SEO.
You mentioned images in your reply to Christy -- could you give a couple of examples of the types of pages and titles you're talking about? In general, image-only pages with no additional content (especially if they have near-duplicate titles) are going to be low-value from a search perspective.