Will running graphics/hardware intesive programs lower the "life span" of an iMac? Specifically, I just purchased a fully refurbished iMac G5 and I am interested in playing several old games on it (most likely Marble Blast Gold and Knights of the Old Republic). Although I know the games will run well on the computer, I am wondering if (generally) running graphics intensive programs will decrease the life expectancy of an iMac (specifically with regards to an iMac G5 Mid 2005 Model) in both the short and long run.

Will frequently running graphic/hardware intensive programs harm (in the long run) an older iMac?

Note- I am not looking for an opinion or subjective account, just some level of reasoning behind why it would or would not impact the computer (i.e. thermal paste wears down, processor runs to hot overtime, etc...) 

I am still new at this so if my question is to vague or opinion based let me know and I can change it.
Mac hardware is designed to handle its maximum load without being compromised, so theoretically the answer is no. 

In practice, as everything electronics or mechanical, if you push towards its limits you machine, every parts of its is subjected to major load and stress.
Wide variation in temperature can provide degradation to silicon properties and may cause failure or T-junction breakages if the hardware temperature watcher doesn't switch off CPU in time. The same is true for GPU. 
From the point of view of HDD and SSD, they have a limited number of writes, and they are very sensible to temperature variation. In fact if you expose for long periods an SSD to temperature higher than 50 degrees, this can half is life. 
Moreover, the more energy you hardware require the more fast you battery will drain, and the more often you have to reload the battery. Here you are contributing to increment the battery load cycles. Batteries have a limited lifetime before they lose their load capacity (it's around 900 cycles).