Most enterprise systems are retired not because they stop working, but because nobody can safely change them any more. Supportability is designed, not inherited.
Five choices make the difference: a clear separation between core logic and country- or customer-specific configuration; automated tests that describe behaviour; documented interfaces rather than direct database integration; infrastructure defined as code; and a team that owns the system after go-live.
This is how SMH Global structures its own platforms: a standard core, country packs for regulation in Saudi Arabia, the UAE, Pakistan and Bangladesh, and a thin layer for each client’s workflows. Updates to the core reach every client without breaking their configuration.
For bespoke development we apply the same discipline, so what we build today can be extended by your team, or ours, years from now.