I felt that the risk of pyometra was a very good medical reason to spay. My little yorkie I had when I was 5 developed this illness and needed an emergency spay op at a late age in life
... I did not want that to happen to either of my girls... not again
so I know I could have waited, and I could have dealt with seasons etc.. but I didn't
and with jessie I feel it was just aswell cos she had a full phantom before her spay... I couldn't have put her through that again anyways...she went from being my happy little girl to a dog I didn't recognise for a while, although I know this is down to her hormones etc at the time. I was told by my vet that if she had one after her first season the likely hood is she'll have more.
so I went ahead...but the spay op was a total diferent story..and her recovery after was fraught with disaster..so whether I would actively choose to put another dog through that op, without them saying it is a total necessity, would be doubtfull