It depends on how hard you ride, and your skill level, combined with how much climbing your doing. I dip chain in molten speed wax every 60 miles. Thats 2 rides and 8000' of climbing. But I used to wash my bike frequently. Shimano 12s drive train, 8100 chain and different hyper glide...
It is a rosenberg connection. BUT its a Shimano part, that fails a lot. Im on my second one, and at the moment they are back ordered. Your local Shimano service center should be able to get you one. Mine is being replaced under warranty, Pretty easy to replace once you do get it.