"He is at a great age now for a goalkeeper; I believe his time is now and he should be playing his best from now on," says Glenn, at Villa Park at the weekend to see him in action for England.
"When you look at David Seaman, who has been a top goalkeeper in this country now for all of 10 years, I would say, maybe longer - he is still going strong at 38 or 39.
"David James is 31 and, the athlete that he is, means he will play as long as David Seaman - so he has got seven or eight years of the best football to look forward to."
David was Glenn Roeder's first signing since he took over as manager - and, perhaps, the most important for that reason, thinks Glenn.
"I always feel that we at West Ham are very lucky to have secured his services and we want to keep him as long as we possibly can.
"I think the first signing was important and it made a statement to everybody about what we were trying to do.
"It did open the eyes not only of people around the game, but of people around the club, and our supporters who were quite surprised that we managed to secure the services of David.
"That is the type of signing you'd like to make on a regular basis if you could get the funds together.
"That is the difficult thing in the present climate, but I am not whingeing about that because I understand the situation that football has got itself into."
Glenn says that it is not natural talent alone that has got David where he is, and adds:
"David is like all top class sportsmen in any field, whether it be a footballer, an athlete, a golfer, a cricketer - he is driven.
"These people are highly motivated individuals; he has worked hard throughout his career to get where he is today.
"He hasn't got there by luck, and he hasn't got there by not working extra hard at his game; it has been a long haul for him.
"He started out as an exciting teenage goalkeeper when I was at Watford; I played in front of him and I have still got the scars to prove it - I certainly had to get out of the way quickly a few times, I know that!"