I fed both ds1 and ds2 (my second and third dcs), who are 21 months apart for just over a year. Ds1 was still feeding at night when I was first pregnant. He substantially increased his food intake, decreased his milk intake, and consequently started sleeping through at about 15 months, after we went away for a weekend and he was too busy to think about bfeeding.
I found feeding a bit uncomfortable, but not painful for the first few weeks of pregnancy.
I did worry about whether ds1 would mind sharing, but when I was about 8 months pg I was holding a friend's newborn, and he toddled over, patted my breast and pointed to the baby, so I guessed he would be fine with it, and he was.
After ds2 was born I had loads and loads and loads of millk, certainly no problems with supply, presumably due to the frequent stimulation.
I didn't mind that I was feeding two babies, but I actually didn't at all like feeding both of them together. When ds2 was very tiny I could hold him in the rugby ball position, pu ds1 across me and feed them both. I could also arrange them and me with pillows on the bed to feed both at the same time. But once I was arranged I couldn't move or do anything, and I felt very bovine, so I tried to feed them separately. I only ever did it privately as it was very exposing
It wasn't all that long (but I can't remember how long) before I was only feeding ds1 in the morning and evening while dh changed and dressed or undressed ds2.
I weaned ds1 just before he was 3 as I had it firmly fixed in my mind that I didn't want to be feeding a 3yo, and I was a bit sick of tandem feeding. He wasn't pleased, but he wasn't distressed either. I think he would have carried on for a long time if I had let him. When ds2 reached 3 I was a lot less bothered as it seemed a bit arbitrary to say "stop before 3" and I could see he was losing interest. He actually weaned a couple of weeks ago at about 3y4mo, but for a while he had only been feeding about 3-4 times a week.
If I were to be completely honest, I'd have to admit that I would prefer not to tandem feed again, but on the other hand, I would also prefer not to wean a toddler who wasn't ready for it. However, I'm unlikely to have another one, never mind two more children, so I don't expect to have to make that decision!