我长期以来都在学习中文。
wǒ chángqī yǐlái dūzài xuéxí zhōngwén 。
I have been learning Chinese for a long time.
他们长期以来一直在合作。
tāmen chángqī yǐlái yīzhízài hézuò 。
They have been cooperating for a long time.
这个问题长期以来没有解决。
zhègè wèntí chángqī yǐlái méiyǒu jiějué 。
This issue has not been resolved for a long time.