I nursed Monkey (who turned two at the time) through my pregnancy with Bee and then until she was 9 months (just after he turned 3). I set out to do it as long as it worked for us.
-I set limits. We were already night weaned and I got strict about nursing deliberately (not sip, play, sip) and in a position that was comfortable for me.
-I found that lying on the couch and letting him have a short drive bye, kept him feeling connected and good to go play quietly for a while and let me rest.
-I got mild thrush from antibiotics and nursing provided just the right amount of friction to scratch the itch.
-my milk sure dried up, then came in around 32 weeks, but he kept on going.
-for me it was never uncomfortable, so I never really put much though into stopping.
-My midwifes were good with it as long as I did not nurse in labour. They said the unplanned homebirths the see are often when mama stops to nurse before heading to the hospital.
Tandem nursing I loved. They held hands and my older one would pat his sister. It was great for jealousy because the could share and have as much of me as they needed at the same time. Only trouble is your are at your multitasking limit nursing two at once, no free hands for the computer.
All that said, I weaned Bee this weekend (by saying no half a dozen times, so she is in a ready sort of place) and am really tempted not to start again. Mostly because she has taken to it so easily, but I am still trying to make up my mind.