I don't think the Greens matter that much, the Liberals and Greens aren't going to force an election unless Horgan pulls out some kind of poison pill legislation they just can't accept.
I don't think minority governments should be held to fixed election dates because it gives complete control of early election timing to the opposition parties, but I think it should be made very difficult for early elections to be called by sitting governments. The electorate gave them a minority and it is their job to do their best to make it work.
I can see that it might be worth it to him as well but it isn't supposed to be about him.