Any chance you can elaborate on this a little? Also, what time frame do you consider to be "long term"?
Investment grade just means that the company has generated profit, is generating profit and should continue to generate profit (or in this cash cashflow). ie the underlying business is making money on its own feet.
Looking at the past 10 years of financial history, ERA has generated cash flow in each year. The number of shares outstanding (ie total shares) has remained constant during this time (so it hasnt periodically during this time been tapping shareholders for extra capital).
So this just means that the company can be 'valued', in a traditional sense.
PDN has been loosing both cash flow and profits for most of the last 10 years.
So it has been reliant on raising capital periodically to pay for these losses. This can been seen by the number of shares outstanding rising from 151million in 2001 to 717million in 2010 (not all of this might have been cash raising, some might have been excersising of options, buying out other companies through the issue of shares, but you get the general picture). Broker forecasts estimate PDN moving to profit (but i dont know about positive cash flow, my screen doesnt provide this information) over the next two years.
So its possible that PDN will become investment grade in the future.
In regards to ERA being a dog. It could be. Even though it generates cash flow, there have been periods when the retention of that cash flow hasnt generated a return above the cost of that capital (ie Cash Flow Adjusted Return on Incremental Cash Employed)
There is no fixed period for long term, but a guide might be 5 years, 10 years.