I know that once you've bought the perfect prep machine then you might as well get your moneys worth and use it. But really, making up bottles is dead simple and no hassle whatsoever. I really don't get why people need a stupidly expensive machine to do it when all you need is a kettle, fridge and microwave.
Holls, what is your DS's weight? I don't know if feeding is weight related or age related but DD is 15lb 8oz (7.05kg) at nearly 15 weeks. I make up seven 6oz bottles (170ml). The tin recommends 6 feeds in 24 hours but I do 7 feeds, she doesn't finish them all though. As an approximate she has the following:
8am - Breastfeed then about 4oz
10am - About 5oz + breastfeed
12pm - About 5oz + breastfeed
2pm - About 6oz
5pm - About 6oz
8pm - About 6oz + breastfeed
11pm - About 5oz
No feeds overnight, even if she wakes.
If you think long term, to when you have a small child eating meals, they generally need snack time as well, at first. I've always found toddler eating patterns generally follows:
8am breakfast
10am morning snack
12pm lunch
2pm afternoon snack
5pm dinner
7pm milky drink before bed.
So I am sort of working towards these kinds of timings for DD bottles. Once we get to 6 months then I will start offering proper food followed by regular bottle at times already established as part of routine.