I usually wash baby bottles and pump stuff in the dishwasher, but they arent ever quite dry after so I'll then put them in a piece of clean kitchen roll to dry overnight, then the next morning assemble them and put them in a cupboard until needed (and at that point put them in a milton bucket).
We usually grab the first bottle or pump set we can reach in the cupboard, which means the ones at the back may not have been used for a few weeks. I just got a milk storage bottle out of the cupboard and there's condensation in it - is it safe to use? Why has it happened - have I put them away not dry enough? I'm not sure I can do more than leave them overnight!