I use it every day.  1200 mg in the morning and 1200 mg at night.
Sometimes, frankly, I use a little more (even though you're not supposed
to) when my secretions coagulate in the dry winter air.

It does seem to help me.  Because when I have forgotten to take it on
occasion, I do notice later that the secretions are thicker and harder
to drain.

Try it and see if it helps you. There is doubt about whether guaifenesin
actually works in thinning mucous.

There is also OTC Humibid now, the same medication, guaifenesin. (The
prescription Humibid LA was supposed to become available again, but never
did.) The Humibid-DM includes cough suppressant, the Humibid-E is only
guaifenesin. The tablets have 400 mg. of guaifenesin, as compared with 600
mg in Mucinex, and are not time-released, as the latter is. So, to take the
maximum dosage of 2400 mg per day, instead of taking two tablets of Mucinex
twice per day, with the Humibid you take two tablets 3 times per day, for
the same dosage. Looking at the price of the bottles, how many milligrams
you get per dollar, Humibid-E is much more economical than the Mucinex. (A
100 tablet bottle of Humibid-E sells for about $20, sometimes on sale for
less. At 6 tablets per day, 100 tablets will last for 16 2/3 days. I believe
a 40 tablet bottle of Mucinex also sells for about $20, but at 4 tablets per
day, will only last 10 days.)