I explain to DS about money, budgetting and finances. So we can't buy him Angry Birds and food - which is going to win? I've done this from a young age: you can't have this because we can't afford it.

Having said that, DS has lots of stuff as family buy him quite a lot, I will buy him books and games to play together when sales are on (so jigsaws, board games, even athletics kits). He has a large box of wooden railway - and I refused to buy him a second system so he could get everything all over again.

For his Annual Big Gift days, I put away most of the toys once he has opened them and picked the one he wants to play with now, so it's like he gets something new every month. Even some of the older stuff is "new" once it comes back into rotation.

However, given that your child is constantly demanding rather than opportunistic or you offering, what other people do with children who don't demand toys all the time is different. DS is happy with a new toy for months at a time and won't ask for a new one straight away (although he pretends all his toys are angry birds/bad piggies atm, so I don't actually need to buy him the plush toys he is after). When DS starts getting demanding, I just say no. He has been rude. If he isn't polite, thankful and realising how much he does have, he doesn't deserve more. I don't like demands and tantrums so refuse to acknowledge them.