For the last 35 years or so, I have used a light coating of grease on my bottom bracket spindles. My concern is making sure I can remove parts when I need to so I grease everything, bolts, spindles, everything. I use feel to tighten any bolts as Chombi suggests. As far as allowing the crank to slide on too far, I figure that if that happened, the front derailleur would need adjustment as that occurred. I haven't seen this happen yet and I have a few BB/crank combinations that have been taken apart and reinstalled many times and used for many years.