thats a good question, I wondered the same myself. even if they are indoor pets they would go into constant heat cycles and would be unbearable to live with. ..can't win..
Yes, thanks, Opus. I'm thinking of discontinuing Jade's annual FVRCP shot due to information like this.
And while not spay/neutering your pet until age 4 might increase their lifespan, how the heck do you stop a population explosion of animals should everyone do that?