Lord of the Rings: Online is celebrating its fifth birthday this week, but Turbine says that it has no plans to slow the game's expansion.

"There are two questions: One is a technical question, how far can we stretch our technologies?" said senior producer Aaron Campbell. "The fact is, we have our own game engine, and we've been growing it and adapting it to modern principals, modern technologies, new game design as we go. We can very much bolt on, reconfigure or rip chunks out as we need to.

"The other direction is more of a design question. When do you get to a point where something feels unreachable? And at the same time, you have a really focused population of players who have hit that capita and are hungry for more, want more to do. You've got to balance that out."

As the MMO has increased in size over the past half decade, Turbine's efforts have partially focused on keeping the experience manageable - for example, providing swifter ways for players to cross the game's expanding game world, but without sacrificing gameplay.

Campbell believes that character levelling requires a similar sense of balance.

"Level cap is kind of a similar thing. You're going to find ways to keep giving players the sense of advancement and investment, and you have to choose whether an arbitrary number or level is the right thing.

"I think that level is a really straightforward way to communicate that advancement and experience to the players, but it's not the be-all and end-all. We're going to continue to provide players with places to enjoy the game, invest in their characters and continue to grow."

A fourth expansion for Lord of the Rings Online, Riders of Rohan, is due this autumn.