I'm presuming this is for GCSE level/around, please let me know if I'm wrong.
Really, it depends on you - how strongly do you know the topics, etc. I would say a good length of time for this is anywhere from half an hour to an hour. This also depends on what you're doing - some days you may do a bit less with just flashcards, other days you might do a past paper.
I think a revision timetable is a good idea, but always bear in mind that it's fine to juggle things around - if you're feeling tired on one day, just leave it to prevent burnout, and maybe just do a bit longer session another day. The same applies if you have more chores on one day.
Some people will say they do so many hours of revision a day, which is fine, but can be demotivating. It's important to remember that having multiple small sessions is just as good.
I would also say that at GCSE level one hour every day in a week is perfectly good, and half an hour a day on a weekday and a bit more at the weekend is also good. When I say every day, I mean nigh on, because it's always good to have breaks.
Hope that helps! This is just my take on it, but I find that this is perfectly fine. Best of luck!
P.S. even if you just do 15 minutes on a weekday, it all helps to reinforce the knowledge. Less time does not always equal less power: or to use a common proverb haha, in the end a drip of water wears away the stone