legos legos legos- what to do about the "I wants"

Kids are dreamers, right?  So, it makes sense for them to think about the things they want- a lot.  Where is the line, though?

Three of my boys love legos.  It's pretty much all they think about right now.  They build the sets they have, they dissect the sets and build new inventions.  They build huge lego "bases" and have battles and adventures.  They involve their friends, it goes on and on and it's great.

BUT, they also want more legos.  No matter how many we have, and we have PLENTY, (we have thousands) they want more.  They browse the catalogs, surf amazon.com and have recently discovered ebay.  These practices are fine with me.  I know it is natural for them to want things.  They are kids, after-all. 

But, where do we draw the line?  How much do I listen to "I want this set," and "I want this mini figure," and "maybe I'll get this set," before I put a stop to it?

They earn allowance for being "good family citizens" and can earn extra money by doing extra chores, so they can spend their own money as they choose.  I think it is OK for them to think of what they want, spend their money, and see what it is like to have no money left to buy more or other things.  But after listening to the "I wants" for a few days in a row now, I am growing tired of it. 

Sure, I tell them to keep a list so they can ask for the sets they want at holiday and birthday time, but the talk continues.

We have 9  more days before school starts and I'd prefer to not have to listen to the retail talk for that long.  So, I came up with a solution I hope will work.

Today I will tell them they can tell one another about the things they want.  If they want me to know about specific items, they can write them down and show me the list at the end of the day.

I hope this strategy works.