The way we'd all want our dogs to go Penda(if not ourselves),out in the field doing whats best! .Like what folk have said she'll let you know when time comes to start slowing her down,that little longer she lies in for,maybe a little stiffness about her movement,all signs but if you know your dog your'll know when.I was out with a 13,14 year old collie x lurcher today and she marked and flushed as well as she ever did,she'll get a day off tomorrow for her own good but if her owner would let her she'd be up for another mooch out on the lamp tonight.