Most including myself just do not attend to changing the brake fluid often enough. As things increase in cost this is not the brightest approach to keeping the costs of repairs needed lower. Down the road.

Unfortunatly Mercedes calipers have tended to be expensive in Canada versus the United States. Shipping costs have also risen to the point that importing them makes them expensive as well.

Bleeder screws are rough to deal with up here in the eastern Canadian rustbelt. I developed a habit of putting a dab of grease on them. Sliding a snug fitting small length of hose over them and adding another dab of grease. Usually with fuel line rubber hose.

As long as the caliper body is cast steel. We have systems using heat to get them loose most of the time if needed.

The aluminum calipers are in vogue today. I understand that less un sprung weight is better. At the same time the bleeder screw issues will be worse especially as they age here. Aluminium being softer will possibly make cores for rebuilding subject to rejection more often for re kitting. I have heard but not verified some calipers for GM trucks are in the 500.00 range for a rebuilt unit up here.