If, over time, the finish starts to look unpleasantly opaque, this can easily be treated with specific restorative products readily on sale.
To clean the surface you can use any of the ordinary cleaning products on sale, but be careful not to use any that are too harsh. Because the wood has been sealed, any stains can be removed, provided this is done in good time.
Prolonged contact with acid or harsh substances cannot be treated. See the table for more information about effective stain-removal.