Each milk painted piece is protected with either beeswax or hemp oil. These are both natural and incredibly durable, but they are NOT plastic, glass or melamine for example. Those are non-porous surfaces that are unaffected by moisture and, in most cases, heat.
Both the wax and hemp oil cure over time. For wax it takes around 30 days for it to fully cure. Your piece may not have reached full cure time so best to limit its use for 3 weeks. (Avoid placing heavy objects on it or anything that might scratch the surface.) Once cured, the surface will stand up to normal use but, like any wood, it can be damaged by moisture and heat. For painted furniture treated with hemp oil, the oil is a 'drying oil' and that means also ensuring it's had its time to cure. Hemp oil protects while maintaining a beautiful and breathable finish that won't yellow or crack like many synthetic poly urethanes or varnishes can.
If you find the finish on your piece could use a 'pick me up' over time, a (very) light sand (220) and the application of a wax (specifically for painted furniture), or hemp oil (depending on the pre-existing finish) will quickly take care of that.
If you would prefer your piece have a professional touch up, please contact us: firstname.lastname@example.org and we will look after this for a nominal fee. Again, much of how your piece's finish lasts depends on you. Protecting from heat and moisture at all times will ensure a lasting finish.
Coasters and placemats should be used on all surfaces.