I also use the breast collection shell by Medela. I think it is useful for me. Because when my B is eating on one breast, then can collect milk from the other breast. I can collect around 15 ml each time, on average.
Even if you don't want to keep the milk, I think it is also useful. If I don't use the shell, I will use a reusable breast pad (I only use disposable ones when I go out), and I will have to spend time to wash it afterwards. With the collection shell, just need to rinse quickly and then steam it and use again the next time. Really convenient for me.
I think it's useful to me. My baby is 3.5 months now and I still use it every morning because I can pump a lot the first time in the morning and the shell help me collect my milk.