Mice are phenomenally good at getting into structures, so I don’t think you can do more than what you’re already doing for prevention. However, a mixture of traps – glue boards, traditional traps and the new plastic trap door variety – should do the trick. If you put these liberally around the base boards and where there has been evidence of mice living/standing, you will knock the population to zero fast. Every time a trap catches a mouse, you need to immediately put a new one in that spot. You can also do an armageddon style approach where you completely cover the floor with glue boards at the door frame into each room. I would be afraid of using poisons as you may end up with the stench of a dead mouse in a crawlspace, and could also harm any pets in the house.