The income from Adsense would depend on a lot of factors. But if it's the same quality of traffic over a period of time, the income would generally be approximately the same over the period of time.
If it's premium traffic, such as USA traffic, then it would fluctuate - if it's shopping / holiday season, it appears advertisers are generally more generous to spend over their advertising fee.
Or if your site has quality traffic, or niche traffic, and if an advertiser is interested in boosting their advertisement specifically for your blog, you'd noticed that the income would also increase, as that advertiser is paying a premium for his ads to appear on your site.