The problem with letting it be available all day is dilution.

Because assume roughly same amount of player participates (maybe slightly more), spreading them over 24 hours will make the number of players trying to do it 1/6 as much at any time. Now, there would be "peaks" and "dead-zones", so this varies, but chances are, even at the peak it will be less than what we have now, by at least half I'd say.

And what happens when there is a smaller pool of participant at a time? The gap between the closest pair gets bigger.

And what does that mean? WORSE matching.

People frequently complain of masuri matchmaking. And now, the match making of this new event. You are asking to make it worse.

Either that, or you plan to cheat the system by doing it during the lowest population time and use alts to feed yourself. Which used to happen for masuri before Xserver(because within a single server, there were far less participant, ergo the pool is frequently empty so you could do that).

Neither of those two, horrible matching or cheating, are desirable results.

Convoy&plunder does have another time slot, just to put it out there (along with TI)

But yes, it is getting a bit cramped. Extension on events that does not have a matching issue could be considered, such as TI, jinchuriki.

I would say convoy&plunder but plunderers would hate that.

masuri, bond have the dillusion problem so can't really be extended. Given the long time thou, they can be shifted. Say shift bond earlier by 1 hour (start&end) and masuri to 1 hour later could work.

sage, fox, space time are short fixed time event either way. So the only "fix" is to move them. And those can't easily be moved as they are placed on the peak activity time (I would assume)