Wouldn't it be better to replace them with another set of lifters?

 

The 2007 likely came with the "b" lifters. Arguably the best lifter Harley has ever made. The later (2009 I think) came with the "c" lifters that were made in Mexico. These are junk. The "b" lifters should last the life of the engine.

 

They have leaked off and that is where the noise at startup is from. When your oil pressure pumps them back up the noise goes away. New one will leak off just the same.