Even though a band might be popular one year it does not necessarily mean that they will continue to endure. There have been numerous number one groups who have faded into obscurity. The ones that stay relevant do so by being aware of the latest musical trends.
It is dangerous for a band to be overly consistent. If all of their albums stay the same then listeners may consider them stale or even old fashioned. One common technique is to base a new album around sounds that are currently popular.
All of the best musicians strive to better their art over the decades. Perhaps the most applicable example of this is Madonna, whose career has spanned forty years. She managed to stay relevant by constantly reinventing herself.
Relevance can also be attained by utilising the latest forms of technology. ABBA have used holograms during their newer live shows. Numerous bands own social media profiles which helps them to engage with fans. On-stage video technology has also been a game changer. However, the most important factor will be the sound of the band. As the decades progress their music needs to evolve.