I would say that you have too many pets if:

(a) you don't have the money to support them (food, shelter, Vet/medical care)

(b) you aren't emotionally prepared to deal with so many animals

(c) you aren't able to clean up after your pets and maintain proper hygiene (excuse my spelling)

(d) you don't have the time or energy to exercise them or have a backyard large enough for them to roam freely