When you lose even a base within 1-2 sectors of ANY factory consider it useless.
Doesn't even need to go that far.
On some maps, the factories sit at the actual frontline, even directly in front of an enemy high alt base (smpizza) and are absolutely indefensible, for example against a NOE con. I have almost entirely given up trying to defend them, I can get kills there, but in the end it's utter pointless. They are going to be down, no matter what, affecting the whole country for hours. I have aslo largely given up attacking them, which I actually did much more than defending.
And whats even worse is the inbalance in placement. On country having a key factory like AA a safe distance back or covered by a Komet base, while another has the very same up front and on the edge of the map.
At the same time, we know lack a larger target that's actually worth putting a big raid together.
It's a travesty. If it really were about giving targets for medium ranged bombers, additional targets with a more regional impactg (zone) would have been the way to go.