I have to ask as I am quite curious. What age did your child stop believing in santa?
The other week my 7 year old asked his Dad if santa was real and husband just told him no he isn't real although he shouldn't tell his little brother (who is 4). Although in fairness we could tell the 4 year old and he'd forget in a few minutes anyway 
The thread about the 9 year old and his neighbour just got me thinking. We live in a country that doesn't really do santa, or does it their own way so it isn't a big deal to us. But I am pretty curious as to when your children stopped believing and if you think 7 is too young.