Between outsourcing and constant technological change, developers have to constantly keep themselves up to date. If the challenge of learning new stuff isn't enough (and it should be), consider that you never know when that pink slip could arrive, no matter how stable your company is.
Of course the trick is to know what to study in your limited time. One metric you could use is search engine terms, such as the Yahoo!/O'Reilly Buzz game. Another popular one is just looking for terms in job requirements posted on popular headhunter sites.
Let's say you're trying to decide whether to learn, oh, just to pick two things at random, either Eclipse or Netbeans. Putting aside which one is better (that's largely a matter of personal preference), which one is more likely to get you a job? Well, the results from a keyword search of dice.com are pretty clear:
"eclipse": 653 jobs
"netbeans": 25 jobs
Interestingly, of the 25 jobs that matched "netbeans", 16 of those also listed "eclipse" as an option, and 2 listed WSAD (WebSphere Application Developer), which is based on Eclipse. So taking out those leaves us with:
"eclipse and not netbeans": 637
"netbeans and not eclipse and not wsad": 7
The Eclipse one would be higher if you added in WSAD and RAD (Rational Application Developer) and other Eclipse based toolkits, but I figured the number was high enough at it is.
Interestingly, if you go out and read some of those Eclipse postings, a good percentage of them are looking for plug-in or RCP developers. Now I know this is a completely unscientific study, but even Charles would have to admit that's a pretty wide gap.
BTW, I just attended a nice talk Wayne Beaton gave for our local Websphere User's Group. He gave a presentation on the Web Tools Platform and the Rich Client Platform. To see his slides check out his new web site at (I'm not making this up): http://www.eclipse.org/evangelism .