If you play a single weapon I guess it's a viable thing to do if you have nothing else to do
Are you talking about Novel farming or the Atlas Ex upgrade route?
I think both are viable depending on your time and interests. I certainly don't think "there's no point in any EP5 content" as your original post says, and if you are talking about that I don't understand why you'd be limited to a single weapon type.
We get 5-7 collection folder slots at a time and a 48-hour cooldown for every sheet that only needs a single item (4-5 buster quests) to be completed so that's more easily repeatable than previous sheets (and the weapons are generally below 300k each at 30-cap from other people doing them already, or barely any more at 35-cap from others getting them as drops!).
Maybe you mean the probably temporary-limited exchange materials like Chronos Eternistone (of which I think we can only get two right now)? If so, perhaps. I expect they'll be renewable at some point in the not too distant future.
for the period of 4 maintenances until it gets blasted away by another weapon which is extremely easier to obtain, which later gets replaced by another weapon in a soon period.
Really struggling to follow you on this one. Do you still mean Atlas Ex will be blasted away by Liberate? Because I'd refer you to everyone else's posts about that comparison, and my own point that it'll be more than four maintenances since you're comparing a mid-late Episode 5 provision with an early Episode 6 Part 2 one.
And even if it was four maintenances, that's still two months. If you want to be under-geared for that long with - in your words - nothing else to do, be my guest I suppose?
Do you see people getting more than one Atlas in a two month period?
Maybe neets can do it.