One thing to think about is that older cats have a harder time getting adopted. It's quite rare for a kitten to languish in the shelter (or worse be euthanized in a shelter that is not no-kill). There are lots of very sweet animals in the shelter with nothing more wrong with them than they are no longer in the cute baby stage....

Though I certainly won't fault you for taking a kitten - my male was tiny, tiny when we got him - probably 7-9 weeks... but he was actually found outside as a feral and was not a shelter kitty. My female was about 6 mos - I had an elder kitty passed away and we really thought the littler one, who was about 3 by then needed companionship. We thought bringing in another adult might be difficult, but a kitten would be more acceptable. (and they are good buddies)