Most lash lift products come in small either single use sachets or you may get 2 out of them plus the lash lift patch tests . As long as they are sealed well after opening they should be effective for one week.
I pierce mine with a pin and squeeze enough onto a spatula and seal the sachet with tape and wrap in cling film.
I would sooner use one sachet for two lifts and try and book them within a week , as I don't do that many.
There are many systems out there , but I trained with "gateway workshops" because of my insurance recommending them and we used eyeluvlashes and it's fine for me. I have only recently started doing them so I can't say if i will swap brands at a later stage.
Put a search in for lash lift and there will be tons of info from other geeks for you. You will be spoilt for choice.
Good luck