You need to lube the suspension bushings about every 10K miles or once per year. They do dry up and they will eventually fail if they go too long dry. Even brand new bushings will be creaky in a few months if they don't get sprayed and you live in a dry climate.
But here is another thing. I keep my ST lubed up very well, and still developed a creak. It wasn't a suspension bushing. It was a ball joint. The lower on the right side. Since they are sealed, there is no way to lube them by design..
What I did was I cut a small 1/8th inch slit in the boot of the balljoint, got some white grease in a pressurized can, got the nozzle up in the cut, and filled the boot completely with grease. My creaking has gone away. But that was a very good indicator that I need to replace balljoints within the next few months.
They make a grease fitting that looks like a needle. It would be better to use that instead of cutting the boot, as a cut may grow. Although mine have not deteriorated since I performed this service.
Lube your bushings with a spray silicone lube, and if it doesn't stop, start thinking balljoints. You can lube them as I did and it will stop.