We have lived aboard for over 20 years in boats that have wooden hatch boards. We lived aboard in Canada in - 20 degree weather on a boat with two hatch boards and it was no problem. Winters we had a "tent" covering our boat. The tent also had a door.
We are currently living aboard in a marina in Eilat, Israel on the Red Sea. This boat has one hatch board and two opening doors. Its very hot here and we often sleep with just the doors shut and the bottom hatchboard out for more ventilation. Come to think of it we often left the top hatchboard out in Canadian summers for ventilation.
We've never considered hatch boards to be an issue for getting off the boat quickly. Although last week when the air raid sirens went off because of rocket fire from Egypt, we were out in the cockpit pretty fast
Manny and Robyn