I'm pretty sure that's not how it will work, only the event and limited type avatars in DFO have a timer on them, remember the Hero belt or w/e in vindictus? And, the avatars in DFO don't expire, at least the ones you can get from Shop.
DevCat made this game while Neople made DNF. Different developers, different games, different cash shops.
Also just FYI, DNF in Korea has mostly non-permanent avatars. DFO had perm avatars because it was based on the Japanese version. So while we got perm avatars, we also got their horrible gachapon system, because Nexon figured that would make more money.
Look at the cash shop of this game in Korea. Look at the cash shop of Maginobi. That's almost certainly what it will be for Vindictus.