I may have the wrong person however if you are the one who was thinking of expressing full time then yes they do come in handy as EBM has to be bathed in hot water to heat, you are not able to microwave as this extracts the nutrients from the milk. I expressed full time for DD1 and I used mine often but only at home, when I was out and about I would use boiled water.

I was lucky enough to pick my avent one up for $6 at a garage sale too