I had Leo microchipped at 6 months when he was at the vets for neutering. I think this is a good time as they can do it without pain. Leo's chip is the Home Again and they are proactive about finding lost pets. I would recommend it for any pet to help get them returned if they are ever lost.
Chloe was chipped when she was spayed. I had my now late Corgi also chipped. The SPCA cost was very reasonable. My city,Elk Grove, CA requires Chipping as part of license.
WOW, more cities should require Chipping as part of a License. All 3 of mine are chipped. Sid came with his and Babs and Cloe got theirs when they were spayed. . . .
Gandalf and Gwenny are microchipped as well as our mini mutt, Charlie. Given that I just saw 3 corgis on Petfinder.com as strays with no chips, I just think it makes sense. Especially since it really isn't very expensive most places.
Wrigley was micro chipped at the shelter we got him from for $20. I think it's worth it. I worry about him slipping off his collar and getting away from me or somehow getting out and this way, I know he can always come back to me.
Roslyn has a microchip. The rescue we adopted her from puts them in all their dogs and pays for the first year with Home Again. I hadn't actually read about any health concerns with them, so i will have to check into that, but i will tell you it gives me more confidence when we are on walks or at parks. Roslyn has a leather break away collar because i am concerned with the choking risk, but i was always concerned about getting her back if she did run away. It is a small price to pay for peace of mind.