I was joking with one of my judo buddies and I said, "so what do you do with a old judoka? Do you take him to an open pasture with trees on the horizon..." He conceded it was hard for the older, injured judoka to continue training, especially with the younger stronger players. He then said, "if aikido got their s%$t together, we would train that.
When I was in Holland in the late 80's I studied with a guy who had done Aikido for 10 years and was san dan - he had previously spent 15 years in judo - he was pretty competent!
Another friend of mine said once "Ah yes, Aikido - old man's judo!"
More recently I had a chap come along for a few classes who has done judo for quite a few years and I think is nidan. He did say that just a few classes had influenced how he did his judo. Unfortunately for our dojo he wasn't able to stay - his kids love the judo, and he doesn't have enough time for anything else.