Here are some things - beyond the already mentioned - I´d consider good use of my time:

• educating, passing the knowledge on to people who might able to help; that also gives extra motivation to keep skills and knowledge honed
• building social networks (e.g. do favors to neighbors)
• Keep learning, even if the new stuff does not give immediate benefit, learning is a perishable skill too

I am learning to play some musical instruments (recreational and keep learning). I started to engage in CAS. That certainly did not improve my shooting skills (some people there consider it normal to occassionally miss a target even if it is a 3' square at 10 yards shot at with a rifle). However it opened a new social circle with great people. HAM acitivities offer methods of communication and contacts. HAM contests are about the only contest (at least the ones I know of) were you must help other contestants to score in order to score yourself.