Gentlemen - I've been using a Hobbico Battery Recycler (great machine). Anyway, at what point (time taken to discharge) should a battery be retired? One of my receiver batteries is now at about 67 minutes. Should I shelve it for safety's sake? Thanks in advance.....

I get leary when a pack discharges at less than 80% of it's rated capacity. The book says 70% but I err on the side of safety.

Yes. Decide based on the percentage of it's rated capacity, not time. If it's a 600 mAH pack, and all you're getting when the pack is cycled is 475 to 500, I'd take it to Radio Shack or somewhere for "recycling".
Dennis-

Thanks guys. Hard to believe that when I purchased the re-cycler I wasn't really convinced that it would justify the expense. I've been using it for several years and was slow to warm up to what information it could present.

I use mine until about 75% to 85% of rated capacity.
Higher number for smaller packs, lower number for larger packs.