Well you've warmed up them before FB got harsh with their policies. Still there is high risk. I don't know how many accounts you're talking about by "loads" mean, but 10 accounts per device is possible with proper warm-up. Aged accounts shouldn't be suspicious to FB if it's been used by you for many years on same device except if you start spamming excessively. But as for the OP, managing 20 accounts with your "solution", it shouldn't be problem. For managing more than 100 accounts, your solution is a problem because many of my accounts got banned when i was using proxy+portable browser. So i had to switch to multilogin and the constant banning was almost eliminated. I'm talking about almost 200 accounts.
