I think I was about 4-6 months, ish, and I went into bravissimo and got fitted. I'm 2 months in right now and cannot WAIT to get back into underwires, but the size/supply/leaking hasn't settled down yet. Like the look of some on that link, one day!
If you bra fits properly (and I HAVE to emphasise the properly, meaning all of your breast tissue is encased in the cup) then you can wear them throughout. Non underwired bras give me no support whatsoever so I have to use normal ones. There are nursing bra brands that make underwired ones (my back is too small for them) so you could try those. here are a few