hmm it depends on the pet for me. special ones i'll raise naturally, but most of them i just age up so i can take adult pics for my crew pages or show poses.
Most pets I just age up, but I've been meaning to get back into naturally raising - I like the way it slows things down and you get to spend time with the puppy/kitten animations, and really getting to know the petz's personality as they grow! It makes the pet feel more special to me.