Show me someone doing park our in there 50s or 60s. I'm with Dan on this one. I'm decent at ukemi, but don't see the point on doing it as it jacks me up and don't see where it is necessary to learn anything of value at this point.
Off topic so forgive the digression, but Kobayashi Yasuo Sensei is in his 70's and still takes koshinage ukemi, as well as doing some of the most effortless suwari waza I've seen. I'd say I have to agree w/ Abasan, about the Ukemi bit.
I'm also a bit confused by the varying definitions relating to IS & AIKI. are they the same, related or different?