For those of you who are not familiar with Peter Weddle and his newsletter and other resources, I encourage you to peruse his site here.
His most recent "eye catching" news letter article was entitled "Retraining is Useless". Weddle sites a Department of Labor study of 160,000 Unemployment Insurance claimants and the outcome...neutral. Completion of training subsidized by the DOL neither helped nor hurt the students.
You can read the full article here. Weddle's article provides helpful advice on what to consider if you do plan on going back for retraining.
The best solution to protecting your career is to stay current, period. Self study and use of that knowledge in a real environment can certain work wonders. Here is a post on professional development resources you may find helpful. "Finding Professional Development Ops"
When was the last training you attended, formal or informal? How did you use that new knowledge? Oh, and why did you want to learn that stuff?