A lot longer than you think, since other manufacturers also use similar screens (eDP is a godsend of a standard), and not everything is completely changed between generations. In fact, I can put 450/550 trackpads into my ThinkPad (common modification), others come with more caveats (putting classic keyboards into 430 chassis needs some modifications, etc.). Currently I’m in the process of acquiring a Core-i7 CPU and 16GB of RAM.
A lot longer than you think, since other manufacturers also use similar screens (eDP is a godsend of a standard), and not everything is completely changed between generations. In fact, I can put 450/550 trackpads into my ThinkPad (common modification), others come with more caveats (putting classic keyboards into 430 chassis needs some modifications, etc.). Currently I’m in the process of acquiring a Core-i7 CPU and 16GB of RAM.