Drift of my TX setup with repaired/updated MKU2424A (without 10 MHz reference) and FT-817 (build in TCXO, IF=145 MHz):
- After 30min warm-up (RX only) the drift is -250 Hz
- After 5min TX with constant 20W it drifts further -100 Hz
- After 10min TX with constant 20W it drifts further -50 Hz
- After 15min TX with constant 20W no more significant drift
Conclusion: After the warm-up phase the frequency should be reasonably stable for most operating modes. This is ok for me.