Galaxy Note is getting slower and less responsive
Such symptoms have often been attributed to the eMMC chip (which is in fact a small SSD that runs a flash translation layer (FTL) software). Android 4.3 added TRIM support to address this.

There exist solutions like LagFix (fstrim) that run on rooted devices and essentially do the same. Cyanogenmod's Wiki has more information on buggy eMMC chips.

However note:
You may want to check your eMMC type first with eMMC Brickbug Check first, to see if you have a known buggy type (where TRIM support is probably faulty).

Some background here, some Samsung eMMC chips are known to cause trouble (they're used in other brands too):
https://plus.google.com/101093310520661581786/posts/2eEd95oN1ZP