We also do this. For us, the limiting factor is the IDE getting slower with bigger files. For IntelliJ+Kotlin the big file handling got better over time, but if files get bigger and bigger, the response times of auto completion and other ide features gets slower and slower.

At some point in time, some dev splits the file to get faster responses again.

Despite this, we have no issues, git works fine and search and navigation in the code is also just fine.