Any daily pot-smoker will tell you that their short-term memory declines after a few weeks of daily/hourly use. It's extremely well known, though perhaps not well documented.
Right, I acknowledge that in my previous comment. I was more referring to the mental sharpness or cognitive ability. I was curious if there was a noticeable difference in critical thinking/problem solving for users while they are not under the effects of the drug itself
The effects on memory are related to the time since you smoked and are most noticeable after 1-3 hours. Basically, you get stimulated at first (during which time you may actually have increased creative problem solving) and eventually you get tired or "burned out". It feels a lot like low blood sugar which is why some people over eat. If you smoke a lot these effects can linger as a sort of hang over. If you smoke every day for years, it might last a few days.
Speaking for myself. If smoking regularly yes, there's a decline, even 12 hours after the high has gone. The more I spread things out however, the greater the benefits seem to be, both during and after. Every couple of weeks would likely be most ideal.