Questions about cats and dogs

Pets age like normal sims, so if aging is off they won't age either. There isn't any way to check your pets age without mods. You can purchase wellness treats from the vending machine at the vet. And if you click the Pet Care tab you can use the "check on pet" interaction to see if they need anything, their icon will show their current emotion, or the pet will occasionally call for your attention with a thought bubble showing what they need.

You can get a medicine crafting station and level your vet skill up, then you could just take care of your furry friend at home :) But other than that, you're going to the vet, either to get the vet to cure them or to buy the treats to do it yourself.

Dogs and cats will age like Sims, so they will continue to age even if you switch households.

If you use MCCC, you could see how many days they have until they age.

You don't need to always take the pets to the vet. If you have wellness treats, that will cure their sickness. You can get wellness treats from the vending machine at the vet clinic or if your vet skill is high enough you can make them on the medicine crafting station.

If your pet isn't doing well, under Pet Care, there will be an option to find out what's wrong. Most of the time, you can tell what your pet needs by the icon above their head. For example, If your dog needs a walk they'll whine and have a leash icon above their head. You can also shift click your dog or cat and click stats and check their needs like hunger, affection, bladder, etc.

Thank you for the tips. I'll try just buying the wellness treats next time and pay more attention to the pets though bubbles. I'll also try the shift click and mccc to see what info can be seen that way.