I am tandem nursing as well, and agree that so far it is great and sucks
My dd has almost completely stopped eating solids, is nursing a lot, and screams for "milk" most times she sees the baby nursing. Her poop is now almost back to bf poo too which is no fun! DS and I also have a little thrush right now, so that is making things all the more fun.
But, I do enjoy the closeness that we have because of it. She also really likes sharing milk with her brother so it is a cute bonding time for them, even though I am uncomfortable and touched out
I am just very grateful that she hasnt resorted to waking throughout the night to nurse like she used to....up until she was about 18 months, she was still nursing about every 2 hours through the night, now she maybe wakes once! DS usually sleeps a couple of 3-4 hour stretches, so that is very nice!