Brasier, I owned Duntech Princess speakers for 19 years, though I no longer have them. The Duntech models do have inserts/machine screws, no idea about DAL models.
Like Rcprince, I found it was beneficial to tighten screws and checked them about once a year. When I did that it was usually the woofers where it made a difference. Never using a torque wrench (!) I simply tightened each one snugly by hand, without trying to bare down a hard as I might.
I do remember reading a recommendation for brass screws but never tried them. Since I kept them 19 years it should be obvious I was pretty happy with their stock performance.
Like Rcprince, I found it was beneficial to tighten screws and checked them about once a year. When I did that it was usually the woofers where it made a difference. Never using a torque wrench (!) I simply tightened each one snugly by hand, without trying to bare down a hard as I might.
I do remember reading a recommendation for brass screws but never tried them. Since I kept them 19 years it should be obvious I was pretty happy with their stock performance.