What should I do with to my side steps?

[Chevrolado]

How long does it actually last before reapplying it again?

Also is this greasy I don't want to step on my step rail and bring into the carpet

Depends on your usage of your vehicle. If it sits out and bakes in the sun all the time, tends to fade quicker. If you garage the vehicle or park in shade or anything like that, it lasts for quite a while. Couple probably get couple months before having to reapply. I just do it every 3 or 4 washes. keeps everything fresh and clean.
It's greasy upon first application, but once it dries it's pretty good. If you are putting it on your steps, I would avoid the main stepping surface to keep from possibly slipping and falling. Hah. That wouldn't be fun.