I have been expressing for the last 14 weeks and I do it straight into a sterilised bottle. I leave the pump attached between pumping, store it in the fridge and continue topping it up over the course of the day. Once full I cap the bottle, label it with the day and use it within a couple of days - never had any problems doing it this way.
Bottles do only stay sterile for 24 hours but it is generally the formula and not the bottle that is a bacteria risk. If you are storing breast milk in a sterilised bottle in the fridge for a couple of days it is very unlikely to breed bacteria.