Whenever you get 1000 points I think it is... or fifty bucks in your account. Surveys are usually between 50 and 300 points and they send you surveys every day but you dont qualify for all so it could take shorter or longer.
Oh and with some of the surveys, watch out, because they wont actually pay you, instead they claim to "enter you in a $25,000 sweepstakes. Bullshit. Make sure you check the survey first. A lot of them are really long and tedious too. But thats what brings in the money!