4 routers in 3 years?! is there any possibility of an environmental issue? poor ventilation maybe or its sat on top of something hot? microwave even? (know that sounds silly) You may just have had VERY bad luck, I would expect 2 years minimum per router but really 3 - 5. I've had my dlink DIR-655 for 2 years now with 24/7 use and a fair few users online most of the day.
As for gamming lag, you want to use the traffic prioritising software that should be on the routers web interface - I think its called EOS on my dlink but I may be wrong - this will allow you to prioritise ports and protocols over others, basically creating a ranking of importance for what the routers routing and reducing game lag.