The other day, when we went to the site of the WTC (I do not like calling it "ground zero") she said she wanted to shop at a discount department store near there, too. I asked if there were seats where I could sit now and then. She suggested that I stay in a coffee shop or cafe if it got too difficult, and that's what I did. That worked well, I think because she knows I am not crying wolf.
On balance I prefer to have my disabilities "not noticed", allowing me to step up from time to time, to mention that some activities might not be what I want to do. The funny thing is that it isn't my own comfort that often motivates me to say out loud that I maybe should opt out of an activity. The motivation comes from how much I hold others back - their comfort. Perhaps this is another reason I like doing a lot of things alone. I can take however long I need to and not feel like I am holding anyone else back.