I think this is a question that you need to be asking yourself. The statement "Finishing Collins' packet" is ambiguous in itself as it depends on numerous factors such as, how many times are you going to attempt the practice tests, how extensive is your prior knowledge for each individual subtest prior to beginning, ect. Like many others on the forum have stated, I'll go ahead and say it myself, if you are expecting Collin's to teach you all the material, you may be setting yourself up for disappointment. That being said, if you are devoting 6-7 SERIOUS hours of intensive studying daily and you're not say, starting entirely from scratch, you should be in decent shape by july/sept.