Mileage isn't the main issue for suspension wear. It's the area its driven that matters. My car was mostly motorway miles throughout its life and suspension bushes were perished. Since i've had had it mostly town driven, ive managed to tear both bushes. Bumps everywhere around my area and I take them had higher speeds than I would if I had a firmer riding car. The same can happen to trailing arms. £60 arms with a cheap bush wont last in the same circumstances as a genuine setup. I have fitted lemforder lower arms in the past which were starting to crack 12 months on.