I have had 3 dobe females, currently 2 are in my home and both are spayed, one was done at 9 months (done later than anticipated due to a rpior surgery she had to heal from) and the other done at 6 months, and my previous girl was also done at 6 months. So far the two that I have now are fine, no problems whatsoever. My decision to spay them prior to heat cycles was made on the medical information given to me concerning mammary cancer and the reduction in the likelihood they would develop it having been spayed before or after having a heat cycle. The chances drop if they are spayed before the first heat cycle, which can occur anytime after 6 months of age. My previous girl, Mysti did have incontinence at an older age, she was 8 when she started developing problems and the vet could not say positively if it was resulting from her early spay or if it was just something due to her age and other medical problems she had. She had a tendency to drink ALOT and it was possible she had some other issues going on besides the hypothyroid and Addisons that we knew about. We were going to have her tested for diabetes and some other things when we lost her to an Addisons episode a year ago in October.
I am one of the people of the opinion of having a female spayed and doing it early if you do not plan on breeding her. For one reason, it avoids certain other health problems later in her life, such as mammary cancer and other types of cancer they can develop, two, it avoids messy maintenance and having to manage that each time she comes into heat, trying to keep them in diapers, and avoiding accidents which can be messy and hard to clean up, and three, there is always the possibility you cannot keep an eye on them 100% of the time, none of us are perfect and the risk of accidental breeding is there no matter how hard we try to keep them safe, it is just better to be 100% safe and spay her.