I recently removed my cast/T-Bird valve covers to finally adjust valve clearance after many years. They have older neoprene gaskets attached with RTV, and are sealed to the heads each time with bearing grease..  The covers have been removed several times over a span of 20+ years, and the gaskets still look like new and have never leaked. They are impressed with the raised part of the iron heads where they seal.
  Since the silicone gaskets must be installed dry, unless the parts they seal have a recessed trough that captures the gasket, frequent disassembly could be problematic, as they likely cannot be permanently attached with RTV (?). I’m also worried they thus may squeeze out of place when torqued (?).