Game Turns

I will generally allow a day for players to post in response to an event, longer if it's a critical situation or I'm AFK.  :-)
If one PC suggests a reasonable-sounding course of action (eg go left at a crossroads) and no one else objects within a day, that's what the party will do.
In combat, if a player does not post within about a day I'll take it they do something reasonable, usually attack, or follow the guidance of other PCs - eg retreat if the other PCs are retreating - and roll for them if necessary.

I will normally assume the PCs are 'taking 10' on relevant skill checks, I may do some rolls for PCs where necessary.