Every shaft and packing situation will be slightly different depending upon the condition of the packing, how it was installed, seated and broken in and the condition of the shaft. If the flax is old, dried and compressed you may need more drips for it not to become hot. The condition of the shaft can also play a role if it is scored. Ideally you should be able to get to no drips at rest but this is not always possible. There are no hard and fast rules except that traditional packings need water for lubrication.
You ideally don't want more than a 20 degree differential from the water temp with a traditional packing but 10 degrees is better. This could be anywhere from 3 - 15 drips per minute while the shaft is spinning.
Gore packings can run as high as a 30 degree differential but still should drip, even if very slightly.
If you plan on re-packing Duramax Ultra-X, Western Pacific Trading's GTU or Gore GFO are the best you will find. You're really best to set it by heat than drip rate especially with old packing and an old shaft.
Adjustments should be made very carefully with traditional packings as they have no memory and once over tightenedd/compressed will not re-bound if they need to be loosened. One nut flat at a time adjustments will get you there safely..