At the end of the day if a dev takes a year for an update and you are still paying them a monthly stipend and you don't think you should, then don't.
If you think you are being taken for a ride, then get off the train.
I think people should, if they can afford to support a creator, but it's also the duty of the creator to the supporters to continue putting out regular work. No matter how small or big. Once you start treating your patrons are banks to pay your bills, but you don't release goods, updates, then you are treating them like chumps and don't deserve their patronage.
I think most devs due to the fact they are based around the world don't really think about what their behaviour has on other creators in the way of attitude for support.
This is why there are so many incomplete, unfinished games out there.
That's why I fall into the "will pay when completed" category not the monthly category.
That's also, when I was editing and co-writing on Bright Lord v1-6. I saw that as a service to gamers as I was playing so many games and not supporting much devs.
I think 6 months is a long time for an update, let alone year.
But, that's just my opinion.