Puppy through 1 yr. old.........Lots of chewing, not reliably housetrained, needs much attention and training, not good choice if you are gone all day.
1-3 Yr. old........ Still acts like a puppy, may or may not be housetrained, will still chew, needs lots of playtime to burn energy, will become bored easily if left alone too long.
3-5 Yr. Old.......Able to be trusted alone in the house for short periods, needs several hours of playtime daily, will become bored easily, will chew from boredom.
5+ .... A perfect dog. Past the chewing stage, reliably housetrained, content to sleep while you are gone, will want to play for a few hours, but will be ready to sleep again when you do.