It has to be in a democracy. Everyone is free to keep arguing for what they think are good ideas, and those who think they're not need to also keep at it. The struggle never ends, that's the civic duty of the people. Having said that, I think you might be missing one important strategy in this:
>They can try as many times as they want but they only have to succeed once, while we have to succeed 100% of the time. This fundamental imbalance is worrying.
Please correct me if I'm mistaken, but you seem to be implicitly assuming that opposition consists solely of attempting to maintain the status quo. In that scenario you're right that it's more difficult to keep the balance from shifting away from neutral over time. However, instead opposition can fight to actually actively move things farther in their preferred direction, and then even if they lose a certain amount of the time that still won't be disastrous. It's not necessary to win every battle if they're not purely defensive, just some of the time. I don't just oppose further efforts to maximalize IP, I want much (though not all) of the current bits reversed and brought back into more historical balance. I support efforts to reduce the terms back down towards 15-30 years (or alternatively to introduce dynamic pricing/terms), to completely eliminate math and business method patents, better fund examiners, etc. That's where the battle has to continue.
Remember, you can flip your logic around there: we only need to get any given bit of overlong or incorrectly granted IP put back into the public domain once. Maximalists "have to succeed" at preventing it 100% of the time yes?