The first question is, what sustains a business, project or platform? The answer to this, is what the project in question offers, that is to say if a project offers little to nothing the chances of survival will be greatly reduced; this is the fate of most coins which are now dead. Most altcoins today we're created out of hype and nothing more, they came with big whitepaper with no tangible thing to hold on to. So once they list and luckily make few moves on the exchanges they start dying off as there is nothing to sustain it. Some don't even get to exchange as the team will come up with many excuses to delay. So to answer your question, an altcoin that will survive or last long term is one which have something to offer to the world at large.