Mineral oil will slow down moisture loss but not eliminate.
I think you should consider sealing the ends with paraffin wax, latex paint or Anchorseal, ASAP.
Keeping the moisture in the wood does not ruin the wood. Turners seal wood pieces for a long time. We want the moisture retained to prevent cracking/checking until we are ready to turn the wood.
How long it takes to dry out is hard to say. Air dry and kiln dry are different. If I recall I read somewhere air dry may be 1 year/in of thickness. Air dry is a slow process.
Slow can be good. Less stress on the wood.
You do want the maple to be dry before making into cutting boards.
Once the wood is used e.g., in cutting board, it will slowly lose moisture to attempt to reach the moisture of the air in the house. This will mean dimension changes. Best if this happens before you cut the boards and make anything out of them.