Ask H: How much developer time to allot for R&D?

Like most of you I'm sure, our team has a never ending list of requests and tasks. We have customers and management to keep happy. We have pressure to deliver these tasks. But as we plow through our backlog week after week, it can sometimes feel like technology is passing us by. Most of us do things in our spare time at home, but I feel like there should be some company time for this kind of work.

I find that management is supportive of this type of thing in principle, but that doesn't always mean they will accept having project work delayed. The other issue is that some developers will take advantage of the time to goof off.

I'm curious to hear from other people if you have a strategy for R&D and other types of "free" time for developers? Or, if you are a developer, how does it work at your company? For example, learning a new language, investigating some new framework or just some wild idea.