The other side of the balance is spontaneity. There are some days that are just too beautiful to waste. My children grew up in an area where is it would snow a few inches two or three times a year. It was beautiful and fun and usually short lived. If it snowed on Monday, it's likely it would be gone by the weekend. Or, if it did stick around, it would be way too cold to enjoy. Though public schools in our area seldom took a "snow day", we had a standing rule. School didn't happen on snow days. When it started snowing we put on Christmas music, (didn't matter what time of year!) dug out our sleds and took to the hills!
Remember your end goal. It is not to get the most information into the heads of your children as possible. Raise your children able to stop and smell the roses-- to notice the things we all miss. Raise them to learn, laugh and enjoy life!
Balance sometimes will mean to play more and study less. Trust me, if children have the opportunity to play, they will have more capacity to learn.