Hi there! I'm a 6th year this year. Personally, I think you should do some amount of study in this year. I usually spent around 3 hours of study excluding homework. It's a lot but I try to have breaks in between maybe 10-15 mins. For me, 5th year is the year you should keep your head down and do the best you can. Learn and do the study for tests and you will be fine. Don't leave it till the last minute, because by the time you are in 6th year you'll be cramming instead of revising notes you already know. It's best to learn as much as you can in 5th year so less work and pressure will be placed on you in the final year.
Hi, personally I didn't remember most of what I studied in fifth year, but that's up to you. What I would recommend is making good quality notes for every subject so you don't have to spend much time on that in sixth year. Then you can focus on making notes for the new topics you cover in sixth year, and revising your old notes. Remember that your results in fifth year don't matter, and you probably won't remember them next year. All that matters is the basis you make for your studies in sixth year. Good luckkkk