I don't think holding back content for a bit and charging for early access is effective.  It CAN be effective at moving traffic to another (free) site, but that's it.  I use such a structure to keep people going to my primary site, and it worked wonders when I transferred over from Smackjeeves.  But charging money?  (I'm assuming you're thinking of Patreon here.)  I've sadly only see Patreon really, REALLY work for those artists willing to do lots of original high-interest content available only through Patreon. 

I've only seen one Patreon campaign for a webcomic that I would consider successful, and there were ... shall we say obvious reasons for his success.