We everyone here (at least the main reason) for learning. I may post sometimes while sometimes I may post 1. Chipmixer is the campaign which pays for 1 post too. If you post only one, you will still get the payment.
Not only chipmixer and bitvest but there are also few number of campaigns out there that are paying per post . some have a minimum limit while others dont have . if you are a campaign that has a pay per post structure and does not have any minimum limit then thats good because you wont feel pressure . you can post as little as one post but that wont be rewarding at all but thats okay if that can make you feel satisfied .