I waited until 9 years/138K miles to replace all four struts on my Subaru and it was too long. One rear strut could not be pushed down beyond the half way mark. the other rear could be pushed beyond the half way mark but would not return beyond half way. The two fronts could be pushed down and would return but at about half the speed of the new ones. The ride is now much nicer and the excessive rear camber appears to be corrected (still haven’t gotten the alignment done quite yet).