There isn't a well established limit. So long as you do not neglect consumption of monounsaturates and clean saturates, you should be fine. A 1:2:1 ratio of saturates:monounsaturates:efa's might be a reasonable suggestion for general health purposes.
Practically, it is more important to ensure a balance beween n-3 and n-6 PUFA's(polyunsaturaed fatty acids). I obtain somewhere between 6-10 grams combined EPA/DHA every day if you want to use that as a reference value.
Remember, the conversion between ALA and EPA/DHA in the body is very inefficient. I have seen a modest 10% conversion rate from ALA->usable EPA/DHA in some studies. Fish oil is a more efficacious supplement in this regard since you get a direct source of eicosapentaenoic and docosahexaenoic acid.
Basically consuming 12T of flax oil per day is a waste of money and valuable kcals compared to fish oil. I would rather use extra virgin olive oil for its positive effects on thermogenesis and protein uncoupling personally. I have Severed Ties to thank for this tidbit of info that he presented over at wannabebig's nutrition section.