I think the issue is revenue and not user forgetting about the website. People remember sites years later. The problem is the business model. People are not willing to pay for the services of a travel planner which is expensive to build, which means your revenues are affiliate or ad based. This is not enough to support the dev costs.

I've just read many comments that show getting traffic is not an issue. Yes it might be more competitive but lots have gotten traffic. The common issue I see is that none of them have been able to generate enough revenues to support themselves, even with good traffic.