Is lifelong learning key for a solid and sustainable career?

Thank you Robert for your valuable question and also to Tamer for his good answer .
I would like to say that life-long leaning is very important for building substantially sustainable solid career ,keep in mind that the learning should be greatly relevant to the scope of career in order to enhance the skills most needed to support the ability of the individual to standout apart from all the others at the field.The fierce competence in the job market globally ,is also can be considered as an exclusive cause for continuous learning for upgrading interpersonal skills and other skills to be at the spot.
Non relevant learning can upgrades the general cultural knowledge of the individual ,will have an effect on career sustainability but not that uniquely great.
Thank you Best regards

Lifelong learning is key for a solid and sustainable career--right we alwayes need to improve our skills for a solid and sustainable career

Hello Mr.
Robert, Life-long LEARNING key for a solid and sustainable career? Very much YES!!! There is no end to LEARNING   Learning is a CONTINUOUS process  A professional needs to be a LEANER, till-end The moment he feels that there is nothing to learn, than STAGNATION starts. 
One should, often, UNLEARN old things to LEARN new things Business scenario is continuously-n-rapidly changing, world is becoming a-GLOBAL-VILLAGE, innovative business modules are in vogue, lot-of-leverage is happening, big-wigs are cutting unnecessary COMPETITION wherever possible  In such a scenario, one has to keep-up the process of LEARNING intact  LEARNING is the only key to SURVIVE, at top!!!

I was hesitant to say 'Yes' for this statement, as this depends on:
1- The relevancy of learning experiences you will have, sometimes, people learn skills that may be irrelevant to the work, although it may lead to new ways of thinking, and 'out-of-the-box' solutions, it would sometimes be counterproductive, as in expanding network or gaining skills for personal gains
2- Following trends (and fads), and have a very general (and thin) knowledge in different fields, which may dilute your advantage above others.
3- Developing set of skills in a very niche industry, which may turn out to be very beneficial to the individual, due to the uniqueness of industry, and the limited number of professionals; however, the career will be vulnerable to the industry performance.
When I think about learning, I always think about it as building bricks, hence, I would say that balancing between vertical (enhance in core speciality) and horizontal (learning about other related fields) knowledge and skills (and lifetime learning) will lead to an advantage for that individual, and will essentially lead to a sustainable career.
Of course, I am only talking about the technical part of learning; there are many other things, like people skills, leadership, team working, decision making and client relationships (to name a few) which are essential part of lifetime learning, and good performance in these would actually land you on an executive career.

This is dead on.
Information and technology becomes defunct so very quickly.
There are always new discoveries one has to keep abreast of the changes to keep up.
Lifelong learning is an absolute necessity.