I hate this whole "she has to earn it" mentality I see around here.
I understand a lot of the guys here have confidence issues and need this false sense of how awesome they are so they talk about making a woman "earn" this or that. But it's crap. It's a crutch that you might need for a little while, and if it works use it, but it's not the type of mentality you should carry around for long.
Can you imagine what a turn off it would be if you met a girl and took her out on a date on a tuesday, but she wouldn't give you a friday because you hadn't "earned" it yet? You'd next that girl in a hot second because you'd think to yourself "who the hell do you think you are? You think you're better than me?"
3 weekday dates before a weekend date? C'mon, after three dates is when I have already decided if I'm going to keep seeing this girl or not.
Weekend, weekday, it doesn't really matter. Yes, you want to let her know that you have an active social life. But if she can't get you on a weekend for two straight weeks she'll know something's up and cut it off.
Rememer, the number one thing girls are afraid of (early in a relationship) is getting hurt. Anything that you do that gets on her "I'm going to get hurt" radar, she's going to pull away fast.
You have to be honest with yourself and her about the whole deal. If you're thinking formulas like this you don't have the right mindset to get in a serious relationship with a girl (assuming that's what you're there for).
If it's been three dates and you can't see yourself seeing her seriously, put her smack in the friend zone.