2004 Subaru Outback -Ac freezes

My AC seems to freeze up every 15-20 minutes, take about the same to “thaw out” or whatever, and then runs cold again. If I run on highest fan setting, it seems to last the longest. But if I lower fan, it almost immediately fades out and just blows regular air. If I turn off for a bit, it eventually blows cold again. Have replaced compressor and various other leaks over the years, but this issue persists and three different mechanics can not figure it out.

Take it to an A/C specialist for diagnostic and repair