[gemy]

I think the timing is important for a neuter - let your dog grow into his adulthood - give the boney plates a chance to close.

If there is an underlying medical condition - such as an undescended testicle - that is a medical/health reason to neuter.

Behavioural benefits are iffy. Some do, some don't after a neuter. The research at this point is equivocal. So basically don't count on it, if you expect a neuter to guarantee there will be no marking, or no humping.

And I would clarify that this is what I would suggest at this point in time for toy dogs. Large breed dogs are different.