I remember Deoskins. I almost bought one of them. They made some excellent skins. I agree they were the best at the time. They inspired many developers to create some nice themes themselves. Shortly after Deoskins, many themes arose and many of them never even hit the market. I remember trying to build a few of them myself.
Alot of theme developers seem to have 3-6 themes on hand. Having a good selection of themes is always nice, However I think limiting the production of the themes a developer sells may reduce the the overwhelming task of continous updates for their themes. One theme is not much work to update on even a weekly basis. Having multiple skins to update will increase the burden upon them, and eventually lose their customers. I suppose its an ongoing battle for quantity over quality. Make a great skin, make the skin better with each update, make a profitable theme. Having prodigious ambitions doesn't necessarily render the most profitable outcome, and may preclude the further production of your business if you fail to keep your products updated.
I think when you purchase a theme from a developer, you should acknowledge the fact that most themes are seldom updated in comparison to how Cpanel updates. I do not think they should rely on theme developers to do updates. I really think these developers should be doing much more than they are (did). With that noted, perhaps you should purchase a theme with the intent of self updating, opposed to relying on them to continually keep updated. Fair or not, this is the reality of what has become of the production of Cpanel themes. If you are too busy, don't know HTML, or how to update a Cpanel theme. Perhaps buyers should look at themes where the developers are favorable in the area of product updating. I am not trying to justify why most developers have been negligent to update their themes.