I think sometimes it's like wine: it takes time. If you want good wine, you need to give it time to mature.
I think three months really is a minimum standard already. If you look at the U.S. Congress, they get the budget eight months prior to the beginning of the fiscal year. Germany gets it five months before. So three months really is not excessive. Within the legislature, I think a division of labour between committees can make the process more efficient. So instead of having just one committee to look at it, the fact that you have the sectoral committees dividing that task amongst them is already potentially a way of making it more efficient.