I have a pro r-o system in my van to which i can fill my 650lt up in aound 3 hours, my tds reading are around 350. it suits me to have it in all in one place
A mate of mine has one of these buget r-o systems to which he has similar tds reading it takes him aprox 20 hours to fill up he leaves it running day and night to fill a 250ltr tank he never turns it off and he has very cheap running costs but he has to plan ahead
Another freind of mine has a 25ltr di vessel full of purolite he works with his wife with two trolley's 4days per week & it lasts them just over a month they use around 3000ltr's per month before having to replace the resin, this suits them because they live in a 3rd story flat & have no where to store their equipment so to have pure water on demand suits them.
So it depends on your buget and what suits you