I have been using a r9 290.It's around 3 years old.How long will it last?It's not overclocked or watercooled.I've been using it for gaming mainly.I started mining recently.The maximum temperature it rises to is 94 degrees.
Use watercooling if you want to go long with your GPUs
It's a bigger initial investment, but it pays in the long-term and the maintenance is less of a hassle than with aircooling imho!
Not to mention you can scoop up cards with a water-block preinstalled for less than ones with fans. If your like me and have to spread them out in your house because of power limitations, then having them quiet is definitely a plus.