It is a good idea as long as it can't be abused. Stuff happens and games may run long if no time limit, unless they don't last that long to begin with.
And on a similar point, are there any "not logged in for X amount of days" penalties? What I mean to say is do you have to actively log in to maintain your supplies? Do you ever run out and suffer a penalty? If so is there a "vacation" mode to keep you paused for a long time?
Are troops outside of your castle safe at all times or do they have to "auto defend"?
So many questions that only time can answer.