running any game or sim doesn't put any more stress on your hardrive than turning your computer on. Once you click on a program to run, the harddrive loads the program, which usaully takes a matter of seconds, and then for the most part you're done with it.

Adding more ram to help the lifespan of the harddrive isn't cost effective.

In normal cases you would add more ram to help run ram hungry applications.

That's just a general answer to your question and technically yes adding more ram in some cases will help but all it will do is shave off a second or two of loading time which in the long run really won't extend your hardrive and it isn't worth the extra money.