A Mac doesn't become unusable overnight, but Apple supports it less and less. Three statuses follow one another, and they decide what a repair shop can still do for you.
Current product. While a model has been out of distribution for less than five years, Apple and authorised centres handle every repair, with genuine parts available. This is the comfortable period.
Vintage: 5 to 7 years. The model has been out of distribution for more than five years. Repairs are still possible, but only while parts remain in stock. In practice the display or the logic board can become unavailable overnight, and lead times stretch.
Obsolete: beyond 7 years. Apple supplies no parts at all and authorised centres decline the job. That leaves independent repairers, working with used or compatible parts — often very well, but without a manufacturer warranty.
The real cut-off is macOS. Apple usually stops offering major updates before a model even reaches vintage status. Without security updates a Mac stays usable offline but becomes risky for banking or work. Always check the last macOS version a model supports before buying.
MacbookCheckr shows the Mac's year and the exact model it identified, which places the machine in one of these three categories immediately — and tells you how many years of repairability it has left.