The striker is approaching the final year of his current deal at Villa Park, having made his first professional appearance for the club in 2006.
But Lambert claims there is no rush to get a new contract agreed, and compared the 27-year-old to Manchester United's Ryan Giggs.
"A one-club man is very rare," said Lambert. "Ryan Giggs was the last one, there are not too many now.
"Gabby has been here since he was a young guy but, as for his contract, 15 months is still a long time in football – you used to not find out until a week before the end of season.
"It's strange in football, there's a long way to go."
Agbonlahor has been out with an ankle injury since October 26 and is set to miss Saturday's clash with Cardiff City, but Lambert revealed the striker is still happy at his boyhood club.
"He's enjoying his football, it's a bit frustrating at the moment but the important thing is for him to be fit for us after the break," he continued.
"At least the break will give us time. It's a ligament thing, he was playing with it and it started to get a bit worse."
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