Most people at my med school spent about 4-6 weeks studying full-time for Step 1. I felt like I fatigued quite a bit by about 4.5 weeks, so 6 weeks may have been a bit much (I may have passed my "peak" already by the time I took the test). I didn't score quite as highly as I would have liked, but still broke 90 on my 2-digit score and matched at my first choice in internal medicine. Ultimately, the importance of Step 1 depends on what you're planning to match in. If you know you're headed towards peds or IM, you can aim for 220-230 and be competitive even for top-10 programs. If you're thinking about derm, neurosurg, ophtho, etc., you'd better aim for 240+ (which may require more than 6 weeks of studying, depending on your background knowledge, test-taking skills, efficiency at studying, and resources like QBank or even a Kaplan course).
You only need about 2-4 weeks to score the same (or better) on Step 2, and not even studying full time at that! I did quite a bit better on step 2, but took it after the match so it didn't matter much anyway.