I have 2 Ruger Standards, long before the MK designation. One I bought in 1957 (the standard model with 4.75" barrel, fixed sights). The other (1963) is a target model with thumbrest target grips, 6" barrel, adjustable sights, and target trigger. They are still shooting and shooting well. I have thousands of rounds through them.

They rarely "need" to be broken down all the way, but I do it sometimes. Once you get the hang of it they are easy to reassemble. I never felt the need to improve them, so I never bought any of the MK series.