What is some good preventative maintenance that I should do on the MPCNC?
I’m dusting/wiping it off regularly.
anything else?
want to make sure it lasts as long as possible.
Use it. Repair and replace parts that break… 
Keeping it clean-ish is good, especially the router/spindle and the electronics. Also pay attention to the bearings, and make sure dust isn’t caking up in and around them. I’ve seen people put brushes on their rollers/trucks to brush debris off the rails and keep debris out of the bearings. Don’t get too nuts in cleaning those, though. They are cheapish and easy to replace. And a real pain to really clean and re-lube properly. If you’re using EMT or DOM instead of SS, you may need to be on the lookout for corrosion on your rails. Some carnuba-based paste wax (a little goes a long way) can keep the rust from getting out of hand. Don’t use anything with silicon, it will ruin the finish of any wood that it comes in contact with. If you’re using EMT, it will probably take a little while for the galvanized coating to wear off where the bearings make contact, and for corrosion to become a potential issue. And if you live in an arid environment, it may not be an issue at all.
Silicone causes issues with wood finishes.
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