Definitely could use a "hard-cap" on the lottery spawners. I always did sort of enjoy camping things for ages even if they didn't ever have the loot for me which I so badly wanted. The random occurrences in this game are just ridiculous what comes to loot and such, but that's another story.
The spawn rate, especially for certain NMs, is quite alike though. I think it took 8-11 hours for Buburimboo to spawn to me one time, while other times it would be around the 90 minutes mark. And this is with a simple place-holder and only a small area. Let's not even venture into discussing about Stray Mary for example. ^^;
All in all, less time wasted into standing around (I actually do a lot of other stuff while standing there so it's not always that much of a waste, especially if you enjoy your time, then it's not a waste at all, but with things like Stray Mary there isn't much of a convenience on doing other things and one needs to pay more or less attention to it) while waiting for trivial monsters to spawn: yes please.