When to finish practice problems

Hello,

Seems like there is a lot of variation on this site, but when I should try to finish the readings by?

I was thinking of finishing the readings by mid december, then work on practice problems until exam day. 

I know it is really early to finish the readings and start practice problems, but I won’t be able to dedicate more than 20 hours per week going into 2018. 

Does this seem reasonable? What may be the other downsides to finishing the readings this early other than burning out/forgetting the material as we head into next spring?

Thank you!