I think it's important to set boundaries for puppies. I have two seniors one cat 13 and my yorkie 12. I spoiled the heck out of them though because I set boundaries for them at the very beginning. They know what's allowed and what isn't so spoiling them is not an issue.
Although I will admit the older my cat gets, the more cantankerous she gets
. She's beginning to break all the rules. When my last cat did this, she her health was in decline and after 15 yrs she past away so I am keeping a close eye on Zoey.
Now that they are both seniors about the only thing I don't give in on is their diet. They both have special diets and no matter how much they give me those sad looks, I will not give them anything else to eat. Everything else, they pretty much get away with.