I know the feeling.

I don't think there's a cut off point.

As long as you make provisions for your companion animals in case you die or become too infirm to care for them, why should you ever deprive yourself of feline companionship or deprive a shelter cat of a loving home?

Years ago, a friend of mine who was in her 80s actually altered her will to leave me her cat (after making sure that was okay with me.) I agreed to take care of Fluffy in case anything happened to Stella, which gave Stella peace of mind -- and in fact Fluffy lived a long happy life, but Stella outlived her, so I didn't have to step in and assume care of her cat.

But knowing that she could trust me to take good care of Fluffy meant that Stella could enjoy Fluffy's company without fear or anxiety about her cat outliving her.