The short answer
A repair makes sense when it solves a defined problem at a reasonable total cost and leaves you with a computer that still meets your needs. Age alone is not enough to decide.
I start with your goal: everyday browsing, schoolwork, business software, creative work, or something else. A device that is unsuitable for that job may still be useful for another purpose. Replacing a part does not necessarily solve a mismatch between the computer and the work.
Bring the model, the symptoms, when they began, and any recent changes. “It is slow” is a useful starting point; knowing whether it is slow at startup, in one program, or only online makes the next step more specific.
The repair estimate should include diagnosis, labor, parts, and anything else needed to make the device useful again. A replacement also has costs beyond its purchase price: setup, file transfer, software compatibility, and time without your usual tools.
My typical residential labor rate is $90 per hour. Parts and materials are separate. Residential repair and troubleshooting pauses after two hours ($180 in labor) for your approval before more time is billed. That is an approval checkpoint, not a promise that every repair can be completed for $180.
A successful repair may fix the immediate fault without changing battery condition, other worn components, or software limitations. I want those tradeoffs included in the decision rather than discovered after you have paid for the work.
Client-supplied parts can be considered after compatibility and condition are confirmed. A part advertised for a similar model is not enough information to approve an installation.
Tell me what is backed up and which files matter before work begins. A repair, a file-transfer task, and a data-recovery attempt can be different scopes of work. Do not assume a device repair includes recovering every file.
The useful result of an initial review is a clear next step: a focused repair, more diagnosis with approval, a replacement plan, or a decision to leave the device as it is.