To pump or not to pump... That is the question!

[Kelbells]

I returned to work yesterday leaving my 10 mo DS with SIL who is a childminder, he is EBF and is fed on demand, with his feeds varying wildly during the day - we had absolutely no routine, he eats really well so we have sometimes dropped day feeds, when he's teething he can be on and off hourly!
Because of this, I didn't bother expressing at work yesterday (it's difficult environment to do so), it was the longest I'd ever left him (10 hours) and I was a bit Jordanesque by the time I collected him but he fed/relieved me immediately and tanked up on milk during the evening/night/morning before I left him again today. My SIL thinks that not expressing while I'm at work (will vary from a few hours to 10) will effect and diminish my supply. I thought it was just for comfort and my supply would just sort itself out as it has all along my demand feeding journey.... So, wise ones, which is it!? Thank you!!

Just to note, I expressed a bottle yesterday evening for him to drink today which he has if he asks for it

I don't think there's a real answer. For some woman it would affect supply for others it wouldn't.
Do what ever you want and give yourself a massive pat on the back for getting to 10 months!

It may diminish supply, but will you even be able to tell if it has, and does it matter if it does? I similarly feed on demand when home but don't do anything when at work. I figure there's no difference between not feeding all day and a child who sleeps through the night anyway. Yes I might have more milk in total if I was feeding round the clock, but does it actually matter? She still happily feeds when I'm home during the day so it's not like supply has turned off like a tap.

I sent expressed milk the first couple of weeks at CM, but dd wasn't bothered at all one day I forgot it so we stopped.

Thank you ladies, good points! You've reassured me that I don't need to stress about it too much, will carry on as we are unless they get explosive!