The place where I work has some bike racks outside with some basic roof on and not much else. That means if it rains it won't fall directly on the bike, but otherwise it is exposed to the elements. Is it ok to store my expensive mountain bike there every day, all year round, for 8 hours/day? Or will it get damaged over time?
If weather is the concern, yes. You will get some damage over time. Most of that will just be accelerated wear of all the normally wearable components. Keep your chain lubed or it will rust. You will go through grips, tires and seats faster. Any bolts that aren't alloy or stainless will rust. Non-stainless cables will rust through.
That is not the only concern though. You will be exposing your bike to a greater opportunity for theft or vandalism, especially when it becomes obvious that bike sits there all day.
I have a bike that lives outdoors all the time (sometimes under cover, more often without even a roof). It's also near work not home so I don't have much kit to maintain it, or access to facilities for washing it. It's old and was very cheap. I've had it about 2 years and it's not much more rusty than when I bought it.
On this bike and this bike only, I use a spray chain oil (GT85). A light spray on a cleanish dry chain and gears reduces rusting significantly, and I try to do this every few weeks at wet times of year, taking the opportunity of a dry day.
I've replaced the brake cables with stainless as the housings had rusted enough to cause friction; the gear cables are just about OK as I'm prepare to tolerate poor shifting on this bike. Rust on bolts etc. is only a surface issue, but I've replaced some with stainless anyway (as I've used anti-tamper Torx as a deterrent against component theft)