How long can I maintain supply?

[mrsjuan]

Me again (DD 5 months: small, fussy, breast refuser)
Since she was 3 months I have been expressing - at first 6 times a day, then 5, then 4 and at the moment 3 times. She's currently having 2 bottles of EBM & 3 bottles of formula per day.

Although she is occasionally feeding directly from the breast it isn't much and I'm getting to the stage where to be honest I think there's more to her life than breastmilk.

I'd like to keep a small supply (if there is such a thing) for if & when she wants to feed at night & I'd also like to keep giving her 1 bottle a day of EBM for the immunity benefits.

Will I be able to keep up a supply doing just 2 expressing sessions a day (morning & evening?) or will it slowly dwindle?

My understanding is that if you feed, or express, just morning and night, it should have the effect you expect. i.e. supply dwindles but remains enough for the demand. I have never been very happy expressing so I am speaking more from a knowledge of directly breastfeeding. Expressing is generally less efficient but may be your only option sometimes.
I went back to work when my daughter was 6 months and maintained adequate expressed milk for her childminder days until she was past 12 months. She has still fed when with me until 3 years old (I am now pregnant and milk has dried up.) In the last couple of years I know I had some milk as she would stay at the breast until recently - but I couldn't effectively express even on the days I was away from her.
I think the real answer is: don't set time limits or targets. The supply will dwindle but just be aware that you have done a great job getting this far. If you are concerned about dwindling supply then I would advise an extra pumping session - you will work it out.