If you: ride regularly every week, ride in the rain a lot, sweat a lot, leave your bike outdoors, then make sure your seatpost gets some movement with some proper bike grease (mark your seatpost position first using electrical tape!!!!). If you don’t ride much at all, and your bike is stored in doors, then just give your seatpost a small swivel but have it greased at least once a year.
If you have a metallic seatpost and frame (e.g. aluminium, titanium, steel), then use bike grease. If you have EITHER a carbon seatpost or a carbon frame then use carbon paste – a sachet costs $5.