I never believed in Santa; I always knew it was just a fun story. Didn't spoil Christmas in the slightest -- I still find it a wonderful time of year!
Our now 5 year old was so terrified of seeing Santas when she was 2 that we explained that Santa was just pretend (she was petrified about him coming in her house). She and her 3 year old brother love Christmas and are fine with it just being "a fun story".
We have explained that other children will believe it's true, and to not tell them that Santa is pretend.
They enjoy it as a story (we put out the mince pie, carrot, etc, on Christmas Eve, and on Christmas morning they accurately! guess that Dad ate the mince pie) ... they like the sense of being collaborators in the story with us.
Someone asked me once "why wouldn't you want them to believe for as long as possible?"
Because if they DID believe for "as long as possible", that'd be well after many friends had figured out The Truth. Can you imagine how embarrassing it would be to be 10 or 11 and insisting that Santa was still real, in front of your eye-rolling friends?
You're not lazy, it just seems ridiculous to go to all that trouble to keep up a complete fiction, doesn't it?!