It's not really a "sandblasted" finish, it's bead blasted (I assume glass beads). Scotchbrite pads are recommended to keep a brushed finish in repair but a blasted finish is somewhat coarser and a Scotchbrite pad will leave a different texture where it's used. In fact, Scotchbrite pads and A LOT of elbow grease can make a blasted finish into a brushed finish. A friend of mine did that to his older Litespeed and the new finish looks factory.

Ti doesn't turn any darker over the years no matter what the original finish. If it gets darker, that's just dirt accumulation. A good automotive cleaner/wax will restore it to looking like new.