We have one older child (14) and of the £ we spend on him for Christmas, I would say we spend about 30% before Christmas but wait for specific requests from around mid-November.
With our 3 younger ones (all under 6), I would say it is more 80% before August. This is because many purchases are charity shop/hand me downs from friends/eBay etc.
Last Christmas, our youngest two requested gifts (when seeing Santa) that were vague and easy/cheap to buy (e.g
a book about animals). BUT our middle son asked (and was desperate for) something that was £80- we spend about £70-£100 on little ones). Luckily (and thanks to bargain thread on here), we spotted the thing he asked for months before and bought for a steal at £30.
But... it did make me a bit dubious about spending such a high % of budget in advance in future. That said, buying in advance allows us to get bargains and spread the cost.
So, how far in advance do you buy most of your purchases and do you leave a certain amount on 'stand-by' in case of specific requests?