Enterprise Resource Planning (ERP) literature concentrates on critical success factors for implementation. More recently, published work relates to ERP maintenance and upgrade practices. In papers concerning all phases of the ERP lifecycle, researchers commonly gather material via case studies of organizations comparatively new to ERP implementation, maintenance, or upgrade projects. This article uses a literature review detailing critical success factors and best practices during all phases of the ERP lifecycle to frame a case study on a large company with a decade of experience in supporting an ERP system through implementation, two major upgrades, one major domestic business merger, and two international business acquisitions. This article catalogs the company's departures and concurrences with the published best practices and success factors over time, as well as the positive and negative consequences of its decisions. The company's experience shows that straying from generally accepted best practices can lead to a successful outcome, and that portraying some success factors too well can exacerbate problems in other areas. [Article copies are available for purchase from InfoSci-on-Demand.com] Keywords: Critical Success Factors; Customization; Enterprise Resource Planning; ERP; Implementation, Maintenance; Strategies; System Upgrade