A single page can last for years. Especially for children, as you may come across an idea that is too "old" for your child now, so just jot it down at the bottom or backside of the page. This is also a great page to refer to when planning birthday gifts.
I think it's also a good idea to have a "children's master gift list," which you can list gift ideas by age... especially great for birthday parties.
You don't have to write ideas down for everyone yet, but do try to title one page per person on your gift list, then when you come across an idea you have a place to write it down... immediately so you don't forget!!
You can also start a Christmas card list, that way you have plenty of time to add to it.
Simple challenge for the weekend:-) Be sure to read the previous post for some great ideas to start making your handmade holiday!