I started doing site optimization work around 1997ish but didn’t start taking on my own clients until 2000. We started TopRank in 2001 and some of our SEO clients are companies I’ve worked with for 7-8 years. That’s a lifetime in internet time, getting to know their business, hitting success goals and receiving referrals for even more business.
The services we offered then and the services we offer now are quite different and one of the issues agencies have to deal with when auditing client hours vs revenue is to decide where the business is profitable and where it’s not. Client business models change and vendors are expected to change along with the clients in order to best serve the client’s needs.