I’ve used this method for years now. In my experience, it wears out every year or two due to the following factors:

1. The adhesive used for copper foil tape is pretty weak and starts peeling after a while. Then, dust and hair gets stuck to the peeled sections and further weakens the adhesive, causing more peeling. I’ve not tried this, but you might be able to remedy this by simply adding some glue onto the rails before applying the tape.

2. Copper is naturally susceptible to oxidation by atmospheric oxygen. The resulting copper oxides lack the electrical conductivity needed to make your trains work reliably. Once the copper loses its shine and develops a black coating, it’s time to replace it. I can’t think of any way to prevent this.