The earlier you join the campaign the better rewards you may get but first you have to make sure that the project you will promote is a worthy one to avoid wasting your time. Always make a research about the project before joining because there are a lot of scam or fake projects out there.
You are right. Joining at the beginning of the period will provide many opportunities to get full stake if consistent. So the consideration is no longer the fundraising period because a quality project will definitely easily reach the sales target. Although the sales achieved can be an assessment of project success, we will not miss the opportunity to get a full stake if you do not join from the beginning. after all the bounty campaign was relative, some began at the beginning of the sale, mid, and even at the same time as a fundraiser. so, just maximize the analysis.