I haven't managed to read the whole thread, but enjoyed reading everyone's experiences and opinions on the first half of the thread. I have used a wheelchair several times now at retail trade fairs. Our trips are basically 3 full days walking constantly. After my long recovery from the first year I went, I decided to try a chair at our second year. Totally worth it. I could focus mentally as I wasn't struggling just to keep up. This year, I was feeling well so I decided I didn't need it - big mistake, a few hours in to the first day, felt like collapsing, used a chair for the rest of the trip. I still had to get up to walk around the stalls as they are too crowded, and I actually had one lady (who had spoken to me a few times as I wheeled around the outside of her stall) look at me in utter shock when I stood up lol I was like yup, a miracle just happened
It was difficult for me to realise the necessity, as I am completely capable of walking. I can walk some distance, although I need rests here and there at times. But when you're talking about a full day of activity, definitely worth it. I agree with @taniaaust1
about if you're limiting yourself, you need one. But you need to think about not just physically limiting yourself but also mentally - if you can't focus on your task or can't enjoy your day out, it's probably worth it. Also avoiding PEM is a big plus. Try hiring one when you next go somewhere like the shops. Gives you a feel for the pros and cons before actually buying one.