Will a lead still qualify for all flow steps if they no longer qualify for the original Smart List?

I have a Smart Campaign with multiple flow steps, like this:

1 - Send Email X

2 - Wait 5 days

3 - Send Email Y

4 - Wait 15 days

5 - Send Email Z

Leads can only be entered into this flow if they haven't purchased one of our products yet.  So lets say on day 10, after receiving the first two emails, they purchase.  Will they still receive Email Z?  In other words, will a lead continue through all flow steps regardless of whether they still qualify for the Smart List?  If so, what's the best way to restructure my campaign setup to prevent the lead from receiving Email Z in this scenario?

I was hoping to get around it by using choices in my flow steps.  E.g., if Purchased=false, then Send Email Z, and if Purchased=true, then Do Nothing.  But my leads need to meet multiple conditions to receive the emails (e.g., has not purchased AND hasn't had any recent contact with our sales team) and it looks like choices can only have one condition each.