I can't see a problem. The high mileage oils usually say on the bottle that they contain "seal swellers" of some sort, but in reality what they use is about 10% esters in the base oil, which do have a very slight swelling effect, but not a huge amount. The major difference in these oils which helps to reduce consumption is the fact that they are thicker than most oils of the same viscosity, they are on the higher end of their respective viscosity range.
Having the little bit of esters in these oils also helps to keep things a little bit cleaner too.
So to sum up, you should have no problems using this oil for a long time. In fact someone with a brand new engine could most likely use this oil from day one and have good results for it's entire life. From what I've seen on the high mileage oils, not only are they thicker but they seem to hold their viscosity better than lower cost conventionals do.