The 28-year old Greek forward joined the club from Manchester City in 2008 after an initial loan and despite having 12 months remaining on his current deal, is keen to remain a Hoops player.
"I enjoy my football here," he said. "I'm at a club where I feel well.
"It was important to me to find an environment where I feel good because I'm away from my country, my family and friends.
"I need an environment that suits me and here I am. I'm not surprised how long I've been here. I always felt I'd be here a long time. I feel great at this club and that means everything to a footballer.
"Celtic made a lot of sacrifices for me and I did for them also. We have an understanding relationship and that's why I have been here for nearly six years.
"I have a great relationship with the manager and, if he wants me, I want him as well.
"I'm still young at 28 and I can see myself here for a few more years. I'd never say no to a new contract, if they offer me something we can discuss it.
"Will I finish my career here? It's difficult to say as I don't know when I will finish. It could be 33, 35 or 37."