Modern SSDs address the issue of wear using a feature called 'Trim'. This is a garbage clean up / management feature built into the SSD's controller.
Any patched Windows 7 includes Trim support, and here's a Windows 7 vintage article that goes into detail about making sure Trim is turned on:
Enabling Trim will make sure your PC treats your SSD right! :)
The lifespan of SSDs are quoted these days in total TBW (TeraBytes Written) and for new units the rating runs for 50TBW to 300+ TBW. So an OS install of 10GB 5 times over is only 0.05TBW... a small fraction of your SSDs life force.
I would expect a slight speed decrease after several years of normal use (including an OS install every few months if you want)
Most new SSD come with a 3 or 5 year warranty, with Samsung's 850 Pro units getting a 10 year warranty and a commensurately high total TBW rating.