I always sterilised in one go then used them up throughout the day. Otherwise each feed will be even more of a faff.
If I were to bottle feed again I would not bother to sterilise, they don't do it in Australia or America at all and their babies survive. If you have a dishwasher use that, otherwise soapy water and a hot rinse, allow to air dry and all will be fine.
I sterilise the bottles I'll need for the next day and fill with boiled water in the evening, leave in fridge and shake in the milk as required. DS is 11 months old, and fine. I sometimes top up the bottle of water with boiling water to warm it up, shake up all the water (before adding the milk powder) to mix it through. I measure out all the powder I'll need the next day too, and store it in one of these powder pot.