I have 8 Campbell's (1 group of 4 girls, a trio of boys and a lone older male), 6 robos (all male - a group of 3 babies, 2 older males and the newly separated youngster Bruce), 3 WWs (a pair of males and a lone female), 1 Chinese and 1 long haired Syrian male. That's 19 in total.
It can be pretty exhausting entertaining them all so I think I'm at my limit. Luckily I get to work from home quite often and I'm not working full time at the moment anyway so I have a lot of time free to play with everyone but there are odd times when I think argh, just leave me alone for a few minutes!!! (like at 2.30am today when I had to separate my robos).
I didn't intend to have some many hamsters. It just sort of happened. 3 of them are rescues that I just couldn't leave behind and I guess the rest of are my hamster addiction!
It makes it easier having groups of dwarves as that means only one cage to clean per group and playtime is together (although everyone gets lots of individual cuddles too). I certainly couldn't cope with 19 Syrians!!!