The changes they are making are long term. They are likely making it only 4 per 12 hours because in the future there will be greater emphasis on other things to do and players won't feel like the game is "do 4 guildleves, log out, log back in when cycle resets".

Anyway, this is a great change for people who just don't feel like logging in on a particular day but can still do their leves when they feel like doing them. I would say this is a great step in making guildleves more casual.