I was intentionally general because without having any insight into the actual design process of the virtual world itself it's hard to be any more specific.
In general terms, it would work something like this - every in game item would need to have a few variables that include Age, Resistance and Complexity.
Age obviously is a way to calculate the time elapsed since the item was manufactured (it would be difficult to apply entropy to planets/raw materials themselves in a meaningful way). The older something is, the more likely it is to suffer changes in molecular alignment, imperfections, etc and deviate from the original manufacture. This would eventually affect or limit how it could achieve peak or optimal performance. Of course this also is related to the next variable, resistance.
Resistance is a way to measure the innate property of a material to degradation through entropy. For example a piece of raw meat will degrade much faster than a steel pole, which in turn will rust and degrade much faster than a diamond. Some materials also age better than others. A 500 year old wooden beam will not have the same strengths and properties as a newly seasoned one, but a 500 year old steel beam should still be fairly close to the original provided it hasn't undergone dramatic changes in loading, stress, magnetic fields, heating/cooling, etc.
And complexity tracks how far away an object is from the original materials that created it. A lump of titanium is not very complex, but a spaceship engine made of titanium is quite complex. Therefore you shouldn't expect a lump of titanium to either fail or require maintenance, but the spaceship engine must be kept in top shape quite often in order to remain fully functional.
Now - depending on the time-scale of Dual Universe, it's highly unlikely that we are going to be concerned with the degradation of simpler things that would normally take thousands or tens of thousands of years to start showing any form of degradation. This would limit us to three basic scenarios in the time scale of a game (even a game that spans a few decades of real time):
Artificial stress and loading: Anything that is made to undergo rapid/sudden changes in acceleration should suffer increased degradation rates. Wings of airplanes, turbines and fan blades of engines, hulls of space-ships, etc. They cannot be expected to last forever with zero maintenance/repairs. Repairs should cost materials and energy - as well as time, but I can imagine a future where trivial, time consuming tasks are automated.
Environmental damage: Anything that is exposed to hostile environments (thermal, chemical, ionizing radiation, etc) must suffer accelerated degradation. This includes anything destroyed by weapons, for example - heck this could even be a way of implementing damage say from energy weapons.. And it must also include the weapons themselves. The gun barrels on large artillery pieces and WW2 battleships for example had to be re-lined after 100 shots or so. Nothing lasts forever and usage = maintenance. This would also include production facilities/machinery - except for the magical "root" machines that allow players to start building the world. You cannot create a fabricator for example and expect it to produce forever without additional inputs for maintenance and repair and "downtime" to carry out said repairs.
Complexity damage: while complexity itself should not be a cause of damage if the engineering is well done, this basically assumes that engineers are human and not perfect, therefore their creations are not perfect. Bugs in software. Zinc fingers on circuit boards. Bearings wearing out on moving parts. Shorts in electric motors. Magnetization of things not supposed to be magnetic, etc. The more complex a system, the more maintenance it requires to prevent a sudden catastrophic (ie - it stops working) failure. This is a boolean condition. If adequate maintenance is provided (including preventative maintenance), the system will work flawlessly - forever. But if maintenance is neglected, the system stops working AND suffers damage.
But exactly HOW to go on implementing something like this is quite, quite daunting. It could make for a game all by itself THAT's why I was vague...
