I always check new Altcoins is from their project first. How ling did the project start. The goal of that project. The Team behind who help that project. Another famous project who follow that project.
How long is the project been in the ecosystem does not matter but what matter is the genuineness of the project. A project can stay for a long time yet it can still fold up. And according to the market strategies, if a business stay long for more than five years there is possibility that, the project can stay long. And checking the goals of the project might not give you the genuineness of the project because there are some project might good genuine goal but behind the scene they not good.