ELO rating and experience I was looking at many players' ELO over time graphs and noticed something interesting. Usually players stay in the same 200-300 bracket through very long periods of time (I'm talking decades here) despite staying active and playing. My intuition would be that experience would have some positive correlation with ELO but it looks like it's not the case. I know many research has been done on this topic but I have never seen this question explored.
To recap: Is there a known positive correlation between experience (games played) and ELO improvement? If there is no such correlation (as I found to be the case through my limited observation), what are the possible explanations?
If you are asking why players don't improve despite decades of playing the simple answer is that the more time you spend practicing and reinforcing your mistakes the more ingrained they become and the more likely it becomes that your level will hardly change..

The principle teaching of the Soviet School of chess as described by Dvoretsky and others is that the key to improvement lies in annotating your own games. 

Only by critically examining the (bad) moves you make can you identify the kind of mistakes you typically make and only then can you take positive steps to correct them.

This is a very active thing to do. It involves putting your brain into gear. Just putting your game into an engine and seeing where the evaluation changes by a big margin and noting the engine suggestion doesn't count. That is just passive.

EDIT: Analyzing and annotating your own games to identify mistakes with the idea of avoiding those mistakes in the future, something the Soviets practiced in the Botvinnik era, is also one of the centerpieces of Axel Smith's award-winning 2013 book, "Pump up your Rating".

Here is his summary of this technique -

1) Analyse your games with a friend; avoid using an analysis engine
2) Annotate the game in ChessBase, and highlight your mistakes
3) Check the analysis with an engine, and update the annotations
4) Write down the mistakes in a text file
5) Collect all the mistakes in a List of Mistakes, where they are sorted into various categories
6) Make conclusions about typical mistakes, and how they should be avoided in the future

Axel Smith also gives examples of some of his own mistakes and how he used this technique to identify them and correct them in his play.