Growing up while I lived with my parents I had 4 cats total.
Since getting married and having a family of my own I had 2 cats Charlotte and Toby for 14 years.
Then Layla who passed too soon from suspected FIP.
Then Jasper who still lives with us.
Then Benji who passed too soon from a suspected HCM condition.
And now Tilly. So still 2. I would dearly love a 3rd but Jasper has major allergy problems and I want to be sure we can actually afford it financially and emotionally before we make that decision (we also have 3 non fur kids).
I've only ever had one living on my own. My parents had as many as 5, and me and my sister ended up inheriting 3 of them.
Funny thing: the oldest cat we ever had (indoors) lived to be 15 with lots of health issues. But one of my parents cats? Our oldest was 90% outdoors , lived to be 15 and only died after trauma (hit by car, very sad). I am 100% certain that with proper care she's have easily reached 20+.
The other cars all only lived to be 7-12 except for one, and weren't nearly as healthy. Odd, huh?
I've had cats all my life so I have no idea how many total. The most I've had at one time is five, I think. Right now I have 3 and that seems to be a good number. We had four up until we lost one and they all got along well but it seemed rather crowded. I think a lot depends on your home - cats need to have places they can be alone IME.