I've had the card for six years, and started out with a $300 limit. Just this year, in March it automatically went up to $500 and just today I went to pay online and noticed it went to $900!!! Whoop whoop!
Congrats! I had a Penney's card back in 2000. It was one of my first cards to establish credit. The limit was stuck at $300 for a long time. In 2004, I sued GE/JCPenney for reporting inaccurate info to the CRA's and sending my account to a collection agency. I made a couple of thousands from them and got my account to list Paid As Agreed with no lates.
I hope you have much better experience with them. I don't carry any GE products anymore.
And in a case of me looking your gift horse in the mouth, given how long you've had the account without an increase I wish they had been a lot more generous with their credit line increase.