Working in a freelance capacity has a disadvantage that some people may not think of — you tend to be out of touch with the industry. This, of course, depends on how voraciously you network or read industry news and technology developments.
Although I do enjoy going into “the zone” and independently cranking out results, there is something to be said about working as part of a group. The conversations you have often reveal tidbits you didn’t know or insights that may have otherwise been lost. I find team chit-chat to be quite valuable sometimes, because sometimes it opens your eyes to new developments, reminding you that you need to keep your skills sharp.
The best way I’ve found to update my skills is simply to dive into a project. I recently had to integrate a design onto a Magento installation, and believe me that was one learning curve I was quite happy to master. Magento is growing in popularity as far as shopping cart software goes, so having experience in working with it is valuable. Reading about something is good for introducing yourself to it, but nothing beats being knee deep in it.