We have a 7 month old shih tzu - admittedly he's got a lot of stamina and drive to be outside to rough and tumble with other dogs but I'm sure an older shih tzu would be past that.

He's just moulded to fit our lifestyle - my mum has taken him out for long periods of time from a young pup so his energy level matches that. It's completely different in the house, he'll have his mad 5 minutes to entertain himself but he's otherwise a VERY chilled pup indoors.

He's also an absolute ragdoll, he'll let you do anything to him, rarely barks and doesn't irritate allergies (my dad has extremely bad asthma and doesn't have a problem with Oscar). He does need a fair bit of grooming I guess, but a groomer comes to our house every 6-8 weeks or so to tidy him up and all he needs is a brush through his fur a few times a week and a bath in between.