I don't think that's excessive. Portland to Washington DC is a flight of several hours. Anyway, better to visit the lavatory than sit and squirm, or worse!
I always sit on the aisle if I can, and I don't think I've ever been irritated at having to get up for someone to get past me. (Certainly not irritated with them, possibly irritated at the cramped conditions of aeroplanes, but that's different.)
There are advantages and disadvantages in sitting on the aisle vs next to the window. One of the advantages of sitting on the aisle is that one can get up easily out one's seat. One of the disadvantages is that one has to get up sometimes so other passengers can get past. I think it's no big deal.