Filter belly o-ring, change in size with time?

[brew4eagle]

It seems that my filter belly o-ring has gotten larger with time. It's getting harder to make it fit in the groove that it sits in. Has anyone experienced this before? The condition looks great otherwise. I've been losing prime overnight and starting to think it may be time to replace the belly o-ring. It's about 8 years old now.
Edit- by "larger" I mean it has a bigger circumference than it used to (or it's my imagination that it does)

 

[Rocket J Squirrel]

Sure, rubber can stretch, especially if you apply a little too much elbow grease when cleaning and lubricating it. 8 years is a good long life; time for a fresh new o-ring.