Becoming a Platinum artist in Rock Band 1 is much more difficult then doing it on Rock Band 2, since you must have two active instruments locally and both must be on expert, it's no surprise this achievement is daunting.
If you're not doing this with another person I recommend the duo of Vocals/Bass. None of the songs on bass are too difficult (Nothing like Green Grass for guitar or Run to the Hills or Won't Get Fooled Again for drums) for the vocals part watch out for Foreplay/Long Time, I Get By, I'm So Sick, and Can't Let Go. Even if you are doing this with a friend I still recommend doing it with Vocals/Bass unless you can consistently beat the harder songs on guitar and/or drums.
Another tip is play the harder songs on quickplay BEFORE you attempt this, there is nothing worse than getting to the final stretch only to get stuck and being forced to quit.
Other useful tips: Take breaks! Take advantage of the fact that there is no Bladder of Steel in this game, pause, don't be afraid of failing if you need a break, there are no penalties. The Endless Setlist is located in Moscow and should be the final event you unlock when it comes to fans and stars. And I cannot stress this enough, play the harder songs before you try this.
I don't recall the total time it takes to complete this but it should be around 4 hours.