I've done a bunch of these over the years, and it varies widely, probably depending on the company sponsoring the survey. Inquiries to e-rewards usually result in being told expect a time frame of up to 6-8 weeks. My experience tends to be more in the 4-6 week range, although a few have posted much faster. The difficulty comes when you have more than one outstanding, and when only one of them posts, you don't know which one it's for.