Amazing "tightening" of bass on cone speakers

I own a pair of old Mission 773 speakers. My impression has been that these still sound "okay" but have seen better days. Today I was reading the owner's manual to check the stated specs. In the maintenance section, Mission suggested that the screws holding the bass drivers to the cabinets should periodically be tightened(they also warned never to touch the screws for the tweeter). I said to myself "What the heck" and grabbed an Allen wrench. To my surprise, all the screws seemed tight but were able to be tightened another turn or so without undue pressure.
I was surprised by the difference in the sound. Not only was the bass much better defined and could go much deeper without distortion, the total sound was transformed, leaving far more interesting timbres to be heard and even the imaging was sharpened.
Having been into audio since forever, this really shouldn't have surprised me. It makes sense that slightly loosened bass drivers would create bad sound. And over many years of constantly vibrating, some loosening could easily happen. However, checking this out had never even occurred to me and I'm wondering how many others have tried this "cure" and (other than over tightening) if you've experienced a downside?