expression
no matter how much time passes
Used to express that something remains unchanged or does not happen despite a long time passing. Often followed by a negative or continuing state.
いつまで経っても返事が来ない。
No matter how much time passes, I don't get a reply.
彼はいつまで経っても子供のままだ。
No matter how much time passes, he remains a child.
いつまでも means 'forever' or 'for as long as one likes', focusing on duration. いつまで経っても emphasizes that even after a long time, a situation does not change.
Combination of いつまで (until when) + 経っても (even if time passes), from the verb 経つ (to pass, of time).