So my idea of pouring them into a big bottle in the bathroom (well maybe one for shampoo and one for conditioner) and shaking them to mix is a bit crass and maybe best kept to myself?
I do this with shampoo. I used to do it with body wash, but I've run down my supply of average body wash, leaving only the good ones left.
I don't use conditioner, but mum insists to keep the collection for her (along with shower caps).
Now I haven't had to go to the shop for shampoo for months. I don't see many women doing this as I'm sure that there aren't many hotel shampoos that they would use regularly on their hair, i.e. versus their preferred shampoo from shop etc.. Many of my female friends and colleagues who aren't international road warriors usually carry their own shampoo (and even body wash) with them to avoid using whatever the hotel provides. (In some cases this might be warranted, e.g. some hotels which have very, very average amenities, but some even do this when they go to 4 - 5 star hotels).
When I was travelling for work and study more often and the accommodation may not include decent amenities (or any at all), I always took a couple of small bottles of shampoo and body wash with me. I also take a pair with me when I travel through airports where I have no lounge access (useful if an emergency freshen up required).
My main problem is that I collect amenities and amenity kits. It's not exactly an easily portable nor space-saving collection (unlike more traditional collections, e.g. coins, stamps, model cars, even teddy bears or cuddly toys). If and when I move out of home, I will likely have to just leave it behind, perhaps just leave it for Mum and Dad to use at leisure (and for me to use when I come back to visit).
I also collect PJs. Thankfully I haven't a large collection. I can always bring a few with me to use as my PJ supply, otherwise if I had to get rid of them then I'd either give it as a gift to someone else (hopefully they are my size!) or donate it.
I am surprised at the number of people who still use bars of soap. I moved to the liquid stuff years ago and thought everyone else did too.
Soap bars are functionally much easier
I suppose there's a potential issue of "hygiene" if you use soap bars and share the shower (and the soap) with someone else (I'm looking at the married couples here
).
But if I have to BYO soap when I travel, I prefer body wash as - in my experience when I was much younger - trying to keep a soap in a soap tray in your amenity bag as you travel is a PITA.
I also use soap when I wash my hands at the vanity sink. Yes, I know many also have moved to the pump bottles for hand wash solution...