I understand its not easy. I am saying we should always push for more. To do otherwise is to enable laziness and greed.
As much as many Devs are honest and hard working, there are also some that abuse the system and forgiving long dev times makes it easy for dishonest devs to milk their patrons.
Also practice makes perfect... therefore over time, as the Dev grows more experienced, their development times should be improving as should the quality of their art! As I said quality AND quantity!
Personally, I think Patreon is a very flawed system. Devs should only be paid when the Art is completed. Paying them per month just encourages people to take their time. They should be paid only when their customers are happy and they should receive a bonus if certain goals are met (such as delivering their AVN update before 6 months pass).
Going unpaid until they complete their project is also important. That way if they are lazy, they get nothing. If they work hard, they get to eat and pay their bills.