When to start pumping?

Kiedis

When did most of you start pumping?  I plan on breast feeding almost exclusively, but would like to pump occasionally so that I can leave LO with our parents to babysit (we have two weddings to attend this summer). I don't want to start too soon, as I've read that it can interfere with supply if you start too early. I believe I had an oversupply at the beginning, but this seems better now (still seem to have a forceful letdown sometimes, but he seems used to this).