Chris I've always had them replaced in pairs, when the nearside rear went on my STI Greives replaced both rear shocks no questions asked, on the 270 the rear struts were replaced as a pair, & now the front nearside has gone, Charlie in servicing had me drop the car in for a quick check on Thurs lunchtime, confirmed the front nearside is duff & it's booked in on Monday to have both front struts replaced. There have been several upgrades but they obviously aint working, I do know someone that has had four sets replaced under warranty & require a fifth but Subaru UK won't entertain him now the warranty has expired, thats even with the garage asking Subaru if they can carry out the work as a goodwill guesture. A nice set of Teins are the way to go but if the cars under warranty just keep returning it to the garage.
Must admit I've always had a first class service from all departments at Greives