This is partly true, but every service needs advertisement, even if they have been operating for a long time. There are services on bitcointalk that have run their signature campaign for years, but they didn't stop, and it is because advertisement keeps your service in the minds of your customers, if you stop advertising, it is possible people might forget about your service and use the ones that are advertising their services.

Returning clients also have to be careful, there have been many failed mixers that were advertising in the forum, and some of them were still accepting deposits even after they failed and were not processing withdrawals, imagine a returning client who is not aware of this info, whatever they deposit is lost for good.