Expressing- supply and demand

[Imeg]

Just a quick question. The baby is 5 weeks old and I started expressing earlier than I might otherwise have done because of concerns about his weight - he seems to be putting weight on ok now but since I've started it is useful to express sometimes so someone else can feed him. I just wondered whether, if I get expressed milk from a few days ago out of the fridge (or freezer), I need to then express a similar amount that day in order to match supply and demand? Or whether the supply/ demand relationship is over a few days rather than a daily thing?
We have given occasional formula top-ups, again because of weight concerns (max twice weekly), and I presume it is more important with this to express a similar amount to maintain supply?

Have you had a look at the Kellymom website. It gives really comprehensive advice about expressing.
I wouldn't set myself a specific amount to express and get into a tizz with it. Expressing is no where near as effective as a baby suckling so not a real indication of your milk supply.
I would be tempted to express 2 times per day, morning and late afternoon and just keep going till your milk flow has ceased.
HTH