I have used it for the whole process in hydro but last time I noticed a bit of a calcium defficiency, so might try something else when they get close to flowering. If in soil then yeah it's fine to use the whole way, but could become expensive if you only buy small bottles. If you are growing in soil there are probably cheaper nutrients to use or just make sure you have a good potting mix and give them a bit of seaweed etc every couple of weeks.