Nobody's said 3 battleships. Assaulting POB should be a confrontation, if you haven't enough of people to back up your base, then why you've built it? POB supposed to be a teamwork.
We had incidents like 15 battleships(plus or minus) assaulted POB for day or two and then it's started to be incredibly boring. While owner was not sure what's RP and not care about stuff, because he got enough of basic commodities to maintain this base for weeks under siege.