O.G. I couldn't say. I've never put 100k on a set of fork springs.
Along with the springs it's mostly about fork fluid. In my mind, the springs keep the fork tubes extended and your tire on the ground, along with the internal dampener & rebound coil. The fork fluid does most of the compression work. If you feel/sense the springs have weakened and you have never leaked fork fluid by substantial amounts I imagine you could add an ounce of fork fluid to each leg [after checking existing OEM recommended levels] to tighten your front end up.
Since air compresses & fluid does not that would help tighten/stiffen your front suspension up without replacing your springs.
Personally, if I doubted my fork suspension I would replace the springs [OEM or Progressives] and then zero in on fluid levels that would give me the ride I preferred.
Buffeting/Wobble: Ya could always pull the windscreen or fairing for a test ride to help determine it's influence to your wobble issue at 90+ mph.
Don't forget to hold on tight!!! Maybe drop to the tank too! We forget just how much force our screens relieve of us of. But, if it doesn't wobble at legal speeds [or slightly over for passing] I wouldn't worry about it until it might. If it's a steering stem issue it will eventually show you its bad manners at lower speeds.
Disclaimer: No liability or risk assesment assumed. Information provided as opinion only.
