Santa.. the big fat lie

Using Santa as a stronghold with my oldest son, has proven beneficial over the years. All year long.. Santa's watching. A friend of mine told my son about the "Santa Birdy" It's a bird, that can see anything my son does, and reports back to Santa. This has also been useful, even though my son hates birds, and I think the mere thought of some bird working for Santa watching his every move may give him the he-be's, but it's still kept him on his toes.
This year, as the holiday approaches, my husband and I have been using Santa a lot! Unfortunately, this has seemed to backfire a bit. Every little thing my son does, is followed by "am I still going to get presents?" He's now become obsessed with being good, and always worrying when he's not. It's gotten to the point that I tell him if he doesn't stop asking about whether or not he's getting presents, then he won't. And that Santa really despises whining, and the constant bugging of his parents!
I guess we're only asking for trouble even telling him this huge lie about Santa anyway. I really do hate lying like that, even though it's for some great big fun thing. He's only going to be hugely disappointed (as I was) when he finds out that there is no Santa, and his parents have just been snowballing him about the whole thing. It's a rather shitty thing to do to a kid.. I'm hoping the fun of it all will out weigh the lies and deceit.. I forgave my parents afterall..