The lemforder is fine. OEM isn't the best either so don't worry about buying an aftermarket arm kit. If I were you, I'd save and do the whole suspension at the same time. It'll save time and effort in the long run. The sway links should help but you could have a bushing problem elsewhere.
Spring and shock lifetime is not definite. Springs sag over time due to the weight of the car and shocks also wear with use. Heavy loads will wear them out faster. With average use, I would change the shocks by 150,000 miles, many people change them every 100,000 to keep the car feeling fresh. But springs and shocks won't make the car turn in much sharper.
An alternative is a bigger sway bar - it will sharpen turn in through reducing understeer but some understeer is good. VW tuned the suspension to be safe for all drivers but you can reduce understeer without being too unsafe. If you reduce understeer to much though, poor technique during at the limit turns will cause snap oversteer.