Thanks, everyone! I didn't realize that this was a pretty frequent occurrence at one point, although it seems to have become a lot less frequent after the 1980s. Some of that may be related to the longer run lengths nowadays. John Lloyd Young and Lea Salonga can return to the show 8-10 years later, and it's still the same run.
And it seems to have become really uncommon for plays. The only example for a play in the past 50 years that was mentioned was Judd Hirsch in I'm Not Rappaport.