I keep them in the conservatory which is attached to the house.
The secret is not to water them during Winter. I still have not watered them yet. When I do I will only give them a spray of water to wake them up into growth.
Must not over pot .. I use shallow bowls for a lot of them.
They have to have free draining soil. Most do not like PEAT.
I put a mixture of small grit with the proper soil which is John Innes. Half and half mix.
Not that cheap peaty compost that people buy...which they call all purpose compost.
I have in the past also used a little washed horticultural sharp sand, but find that hard to get hold off now.
They do not need much food....Just a week solution of Tomato fertilizer which makes them flower. ( Potassium) 'Tomerite' or Cacti fertiliser twice a year.
128 kinds of only one Species...There are many species including Succulents which come under the Cacti genre.
They must be called by their Latin names because nicknames can mean more than one type of cacti.
I use to belong to a Cacti Society which had speakers come from a far distance to show us their slides of visits to America collecting seed. They are always on the look out for new species. They find a lot of land fenced off and sometimes ask permission to look for Cacti.
Some of my Cacti are 30 to 40 years old.
Echinopsis is mainly a fairly hardy species, but some are hard to keep.
Some are extremely slow growing, and do not get very big.
Some get very large and a crane is needed to lift the pot.