Four seems fine to me, I think as it is most people are going to have more guildleves than they can ever get through.

The boring factor of guildleves will keep most from burning through their entire allowance every 12 hours, especially now that there is no incentive/rush to get them done before a reset.

This is a wonderful change, no longer will guildleves feel like a central part of playing the game. Just an option there for the few who genuinely enjoy them or those who want something quick to do (can't find a party, short on time, anti socials etc.)