In my opinion, sponsor as much affiliates as possible and give proper guidance to the active ones. Help them to become EA and Team Leaders and encourage them to duplicate this process.
On an average, about 1-2% of affiliates are getting active. Of this small percentage, a few are getting serious about this business. So, sponsoring is a continuous process. Do not limit it to a fixed number. If you stick around a few people and if they suddenly dropout, what should you do?