Many times over the years Nathan.
A Pan Am 707 that overran was repaired in H191
A Pan Am 747SP that broke its wing landing gear on landing.
BA, Thai, Evergreen, MAS cargo and many others I cannot recall engine changes.
ATA cargo and JAL sheetmetal repairs.
These are only the ones I can remember. There are many many more over the years.
An engine change isn't considered a major repair. Just another maintenance task albeit a heavy one.
Why do you consider it a convenient time for Emirates to have an engine change?