Milling plastic and soft wood is fine-- avoid metals. I have that same DP and it works quite nicely for the electronics shop and some minor gunsmithing. You prolly didn't realize this when you assembled it but you should remove the chuck arbor, spray it with Simple Green or 409, or similar stuff. Wipe it very clean and then use 0000 steel wool. Now wipe it again with a cloth ever so lightly coated with WD40. Do the same for the arbor's quill up inside it. When finished, place a small 2x4 on the table, insert the arbor into the quill and use the handles to bring down the chuck onto the wood. Force it fairly good so it stays put in the quill. Now it won't rust, won't fall out from vibes, and you can tap it out with a hammer if need be.
Next get yourself a LINK BELT from Rockler, similar woodworking supplers, or a local bearing/belt supply company. Throw away that awful stock drive belt and install the link belt. You will notice a serious improvement in performance from better torque, way less vibrations, quieter running, and less belt stretch. All that from a link belt that will last longer than the machine will. The factory Chinese belt is absolutely awful and way out of tolerance. The DP's bearings will last longer from less vibes. They are sold by the foot and aren't cheap to buy!! But for machines, nothing on earth beats them.
**broken link removed**