Look carefully at the brown ends. The spikes of the burrs eventually shrivel up and turn brown, but that's not the "brown tips" some speak of when deciding when to harvest.
The "brown tips" you'd be keying on is on the cone petals themselves, and if your cones are at that stage, it's pretty much time to pick them regardless of other factors, because they've hit their peak and are going to head down hill soon...
Cheers!