Front Suspension Knocking/Bottoming Out -- Long term fix?

I have a 2005 Volvo S80 that has a suspension problem. I’ve had this into the shop 5 or 6 times now (3 different shops, including the dealer) but it keeps coming back. The symptom is a knocking sound coming from the front driver’s side wheel when the car is going over small bumps/variations in the road. My car isn’t heavily loaded (it’s usually just me and one other person with no cargo.) When I’ve taken it into the shop, the diagnosis is that it’s something wrong with the control arm and/or a control arm bushing. The last time I took it in, the shop said the problem was on the right hand side, they fixed it, and the sound went away (they had previously fixed the left, and when I took it in I thought the sound was coming from the left.)

I don’t drive on gravel roads, and while there are occasionally small potholes and manhole covers that the car encounters on the city streets, none of my friends, family, or coworkers in Omaha have recurrent suspension issues. I also don’t drive aggressively and I avoid hard braking. How should I go about getting a long term fix for this? I’m tired of having to take it in every 3 to 9 months for the same suspension problem.

It could be the strut bushing. My Toyota Camry that has a service bulletin on driving on bumpy roads causes a rattling or bumping noise.