I'm riding a century next weekend with a friend who had a shouder replacement almost exactly a year ago, and he's been riding for at least six or seven months. I haven't talked with him about it since Thanksgiving, but at that time he said he was feeling good and looking forward to canoeing in spring, too. He's a serious paddler, doing a couple of multi-day hard tours every summer.
Just in passing, your husband's refusal to ride a recumbent if that's what he ought to be doing strikes me as, uh, dumb. All of us have to adapt to the ravages of time and our changing bodies, and if a 'bent could give me another 10 years of cycling, I'd jump on it. My dad, who died at 83, had some balance problems after he turned 75 that took him off the bike. He bought an adult tricycle and rode it 75-80 miles a week for most of the rest of his life. He admitted he didn't like it, but said, "What am I going to do, sit down and wait to die?"