Replacement parts

Hey I'm new to CNC and to Stepcraft. I've had my 840 now for about 6 months and have really enjoyed learning and creating with it. Unfortunately I've had several parts that have already wore out or broken mostly due to operator error.

After ordering replacement parts I'm realizing that the lead time for shipping to the U.S. seems to be several weeks out on some items.

So my question is, what parts have you guys had issues with. I'd like to have a few replacement parts for the most commonly replaced parts on hand so the machine doesn't need to be out of commission for several weeks at a time. I've already taken care of the timing belt and I'm sure that will be the #1 response here but what other items if any would you recommend stocking up on?

Thanks in advance.