You'd be surprised man...I change the strings to keep them feeling fresh and easy to play. Old strings accumulate dirt and corrosion and as they stretch out over time they lose their elasticity.
The end result is you get a darker more muddy tone from them, it becomes harder to bend notes, and most importantly it just feels more difficult to play overall. Not to mention the fretboard ends up covered in dirt and sweat from the old strings....
Read this and you'll start to find out how important guitar and string changes and general maintenence is.
IBANEZ RULES Clean and Setup