To be honest, I really do not know if exercises of the pelvic floor would make that much of an impact. I imagine it would as much as it would for someone who still has their rectum/colon.
This is all pretty much of an unknown, and I am not sure what studies they have done that could prove anything one way or the other, since you need to have had both vaginal deliveries and be elderly with a j-pouch to know what that impact is. All the studies I have seen were short term, not long term.
They already know that rates of incontinence issues rise with age and particularly if you had vaginal deliveries. Much has to do with the size of the baby, if there was obstetrical injury (forceps delivery, rapid delivery, etc.), things like that. If there was tearing, that heals quickly if repaired properly, so that is pretty much of a non issue. It is the stretching and stressing of the sphincters and other pelvic floor structures that are the perceived problems. Look at all the women getting bladder slings and repairs due to cystocele and rectocele. Most of them do not have j-pouches, just vaginal obstetric histories.
So, like everyone else, I am just going to have to wait and see how things go. I am hoping that the tendency toward constipation as we age will actually work in our favor in the weak sphincter department! I should be better about doing kegels, but alas, I am not
I can tell you about me in particular though. It has been 18 years since my j-pouch surgery. I am 58 now and post menopausal. I have both cystocele and rectocele due to a very large vaginally delivered baby (9lbs 15oz), with outlet forceps delivery and 4th degree lacerations. This was after a prior c-section for breech 2 years before that (back then VBAC was popular, not so much these days). I have had no pelvic repair, other than the repair done immediately after the delivery. So far, I am continent, but do get the occasional minor urinary stress incontinence. So, I am hopeful... I don't think there is any one right answer.
FYI, here are a few more recent studies indicating that incontinence/leakage is more common after vaginal deliveries. The last one is from the Cleveland Clinic (2005) and that was the one I was most familiar with:http://www.ncbi.nlm.nih.gov/pubmed/22275287http://www.ncbi.nlm.nih.gov/pubmed/16779880http://www.ncbi.nlm.nih.gov/pubmed/16142432