Ignition coils should last between 80,000 miles to 100,000 miles and sometimes longer.
Usually when the ignition coils go out then you'll notice misfires, engine running rough, loss of engine power etc.
If you think your ignition coils are going out you can have a tester put on your vehicle to see if the coils are actually going out.
If the ignition coils are going bad they should be replaced before they do completely fail because when the ignition coils do fail it will leave you stranded.
If it's been 100,000 miles since you replaced your ignition coils then it's time to replace them again even just as preventative maintenance.
For a lot of people it takes 8 to 10 years to reach 100,000 miles of driving so by then it would be a good idea to replace the ignition coils anyway.