I tend to spend a lot of time planning (almost as much as coding). I do tend to notice big changes over a period of 2-3 years but areas where I can notice improvements in say six months.
I think I spend too much time planning and not enough time just getting shit done. It's one of the things that I feel like I have to work on this year.
I don't think it is necessarily a bad thing. I spend a lot of time planning because I find my coding productivity is higher. Often it's better to let problems sit for a bit than to code then first, or if one does a mock-up it is an exploration that is part of the planning, to be discarded and done right a second time.
But what this means is I rarely come in the next week and wonder what I was thinking (it does happen, but rarely). More often I look at things, over a few months figure out better solutions to coding problems and my style changes accordingly.