Mount gach mounts: How long they last?

i've been wondering if it's true that there are permanent ones, i've heard yes, but haven't seen a single good answer

I got one from gach, haven't used mine though but there's no day limit written on it. My friend has an Owl, he has already activated it & has told me that it does not expire (he also activated 2 90-day mounts which have dates on them in the skill invent).