Since my heart operation several years ago I am under doctor's orders to get up and walk around quite a bit during flights in order to avoid DVT. I, too, always take aisle seats.

The one time that I was given a window seat (last minute upgrade) I briefly explained the situation to the woman in the aisle seat in order to give her the choice of switching seats or being disturbed numerous times.

She chose the window seat and thanked me for being courteous enough to give her the choice.