When I first started juggling three balls I used to juggle every day, sometimes as much as six hours, never any less than two. I'd always start by practising every trick I knew for twenty repetitions, if I dropped or fumbled once on any trick I started again. After that I'd try something new. I learnt at least a trick or new combination a day for almost three months. It got to the point where I could go through every trick I knew for twenty repetitions most days without a drop in just over two hours.
I created a dependency for myself on the routine, if I stopped practising for a couple of days my confidence in my ability dropped. I needed the constant daily reminder of what I could do; otherwise I found it hard to believe I could pull off a hard trick when I needed to in front of an audience. Not a bad thing if you can stick to the routine, it certainly keeps your attention focussed, develops consistency like no other way I know & keeps your self confidence high. I suppose you have to be addicted to juggling in some way to be any good at it.
I stuck to this regime for nearly a year I think. I enjoyed it at first, then it became enjoyable hard work, I stopped before it became a chore. I still haven't completely given up on the routine, I still practise twenty repetitions of every hard three ball trick I know probably once a month or so.
I certainly don't regret the way I used to practise. It made me into the juggler I am today. Through it I became noticeably fitter & stronger & I learnt patience, relaxation, passive concentration, self discipline & some really cool tricks!
Nowadays my practise is completely different. I probably don't do six hours in a week let alone a day. Now almost all of my time is spent playing with new stuff. I will often wander round my room playing with one or two props & without thinking I'll stumble upon something new which I will then think about trying to fit into a juggling pattern. I still practise lots of my old tricks & I can still manage twenty repetitions even if I haven't practised the trick for a couple of months. Now though if I drop or mess it up I'll just give it another go, breaking the trick down into smaller simpler parts or move onto something else completely if I've had enough of it for a while. I mainly concentrate on creating a nice shaped pattern, consistent throws to the same height, clean catches, no jerking arm movements. I don't do any timing or counting my throws, I'd rather be able to juggle a short tidy pattern than struggle under a mess of misdirected & out of time throws for a longer time.
For me this style of practise is the most enjoyable I've found. Many other people have other ideas of how to practise. Some people will stick at a single trick until they get it solid then pick another one & work on that. Some people set themselves goals to achieve & plot their progress on charts. Others will practise tricks one throw at a time making sure they always finish cleanly, five throws of five balls & five clean catches, then six, then seven & so on. No way is particularly better than another, they're just different. Underneath it all the only thing that makes a better juggler is practise, regardless of how you do it. If you are going to do a lot of practise the best way is the way you find most enjoyable. Follow your enthusiasm.