an American couple has lived together for 65 years.---Has been living together for 65 years--present perfect progressive 现在完成进行时, to emphasize that they are still doing that today.
A past perfect should be used when talking about soemthing didn't happen in the past:
如果外出不穿上情侣装，彼此都会感到“不舒服”
yours: They both felt "uncomfortable" if they didn't match their clothes when they go out.
--They both would have felt "uncomfortable" if they hadn't matched...
如果外出不穿上情侣装，彼此都会感到“不舒服”
If just for generally speaking we shall use present tense: They won't feel "comfortable" if they don't wear matching clothes for couple.
