Speaking to a reporter at the Hard Rock Cafe in Stockholm, Sweden, KISS bassist/vocalist Gene Simmons discussed the idea of retirement.  Simmons acknowledged that it would all end one day.  He went on to say:

"I hope on the day that we end, we end on a high note instead of going down.  You don't want to stay one day longer than when it's great.  You want to be great 'till the end...We probably have another 5 to 10 years at the most."

Of course, what Simmons says should be taken with a grain of salt.  As the reporter mentioned in the video, the band's "farewell tour" was 13 years ago.