Old Dog New Tricks Follow-up

After 3 weeks of encouraging our our 14 1/2 year old Yorkie to "shake," we seem to be making progress. Fergie raises her right paw when asked to "shake" before she gets her treat every morning. It has taken longer than it would have when she was younger, but, it appears that it just may be possible to teach an old dog new tricks. What do you think? Have you had luck training elderly dogs?