Of course animals will eagerly reproduce. I never plan to breed him. It is much better to perform elective surgery on a relatively healthy ten or twelve year old pet than to wait until they are fourteen and in need of emergency surgery. Potential risks to your pet and associated costs are greater if surgery is delayed. It is a minor hassle to tote your pet to the vet to get them neutered.
Current anesthetics are safe for all size pets.
Surgery on smaller patients, in fact, is often easier than in larger ones. We perform surgery on one hundred gram hamsters and on two hundred pound mastiffs. We do take extra precautions with smaller patients, especially making sure that they stay warm during and after surgery. I don't know a single vet who would not prefer to spay a four pound Pomeranian rather than a one hundred pound Labrador Retriever. A neutered pet may be a little more likely to become overweight than an intact one.