Is money earned from affiliates “seasonal”?

Over the last month or two I’ve noticed that revenues generated from some advertisement services seems to be getting seasonal. What I mean by that is that during certain months of the year, either the revenues generated shoot up or it comes down significantly. I’ve seen this trend now over a two year period and am wondering if others have noticed a similar trend. I’ll really be interested in knowing this. Do share your thoughts.

So far the only trend that I noticed was that traffic on my site dips during weekends. Which I can understand completely. If traffic increased over weekends, I would really wonder if people are so hooked to the Internet that they couldn’t find something better to do with their weeekends ;-) No spam here please. Its just a joke… :-)