You should not be experiencing multiple shift solenoid failures unless one of two things have happened:
1) Transmission or engine main harness has damage. Usually abrasion on a metal corner, or a heat damaged connector. Or sometimes the harness even melts through.
2) The transmission has been trashed (bad tuning or stuck turbo vanes) and debris is getting into the solenoids. This would be easy to see by looking at or smelling the fluid. If it doesn't look cherry red, or it leaves sparkles on a rag when you wipe off the dipstick, I'd suspect other damage.
2000 E450 dually V10 wagon