It is my feeling that its very difficult to run any metallic ink up to full strength, for more than about 1000 impressions. The suggestion for a double hit of metallic was a good one if you can spare the extra unit, extra plate, extra washup, and extra time. If its a run of more than 1000 impressions ,I would suggest taking either a half step, or even a full step up in the PMS book. For example.... your customer specs pms 872 gold. You load the fountain with either a 50\50 mix of 872 and 873. Or you could just take a full step up and run 873. The step up will not give you a true 872 hue but it will come pretty close WITHOUT the inking problems associated with running the spec ink. The higher number will be a richer color that you will be able to better control when run down a bit, resulting in much more stable inking. If you decide not to tell anyone about your color swap you can be pretty certain that nobody will notice. I won't tell if you don't tell!!!