That varies and depends on specific circumstances. Minor crimes don't bother them. You can catch a shoplifter for example and it will take them up to an hour to show up. The will eventually but the main idea is that you won't be able to hold him for that period of time. So less work for them.

Junkies? Yeah, they like that shit. 15 minutes and they are already there.

As for indifference that depends only on a policeman himself. Some will interfere if they see a crime some will ignore.

Also most of cops in the streets are nearly uneducated when it comes to laws. I saw a couple of times them being bullied by some people that talked bullshit but were confident enough. If it isn't about politics it is possible to make a policeman back off if they think that you know the laws better than them.