Longer anyway then the intake. Poor fuel and short rides can cause damage, additives on the other hand can clean injectors, pumps and fuel lines. Motorbikes with fuel injection have an "Fi" warning light. Injection itself can be far from accurate when millage or performance goes down or is lost. When it fails though, the warning light will be on and the board computer will have a readout ready on exactly what malfunctions.

How a motorbike is used and maintained will determine what it suffers. The Internet can be a great source on finding what components have failed on owners of specific vehicles and at what interval. Often you will find solutions and useful advice. One thing I have run into on forums lately is injection failing because of a defective crankshaft position sensor. These remain vulnerable so keep that in mind for when you have fuel injection and the bike is not reliable.

The service manual of a motorbike specifically, may point to parts that require attention and offer a detailed chart of service intervals for injection components. Owners manuals don't cover much.

unless its damaged physically or the fuel delivery system is gunked up by using cruddy fuel or letting it sit, it will likely last a very long time .. if anything the pumps tend to be the weak link

It can work for the life of the bike. There is no way of telling.

Forever, theoretically. Anything can break, but you can fix it too.