I normally won't spend a long time looking for a disc. If the disc is irreplaceable...yeah. But honestly I don't have too many of those in my bag. If the disc is going to be a pain in the butt to replace, that is another story, I will put in a bit more effort.
Overall, I try not to carry expensive discs. If I go to a course where I know losing discs is a regular thing for most people because of the terrain, I will leave those discs that are $20+ in the car. A wise decision which I rarely think of ahead of time, is to switch up your bag before you even head to one of those treacherous, mountainous, black hole type courses.
15-20 minutes is normally when I let the disc go emotionally, I will hold onto hope that someone will call, but that is mostly to help with the mourning process.
TIME IS MONEY!! Most of my plastic is not over 20 bucks, if I look for a disc for an hour and don't find it, I just spent 20 bucks to work for an hour. That is counterproductive and honestly depressing.
If I look for the disc for an hour and find it, well I just worked for an hour when I could have been disc golfing. That disc, in a way, now cost me 35-40 dollars. I mean it's nice to get your disc back, but you understand what I mean. Like I said, most of my discs are in the 15-10 dollar range and I can have them shipped to my front door with only a few minutes of work (clicking and typing).
I will admit that many of my discs are dyed and if I love that dye, or I have a special attachment to the disc I will search longer. Also, if the disc is visible, I have a strong belief that leaving it behind is wrong. I have done it and regretted it later. Unless it is out of reach with my retriever or is dangerously high up in a tree, I am doing everything I can to get it.
In the end, discs are plastic and PLAYING disc golf is more important to me than finding the piece of plastic buried in the goose crap at the bottom of the canal. I have friends who will rip their clothes off and jump into the water like maniacs, and I think it's funny. But I also have a friend who did that, cut his foot, got an infection and threw down 10,000 dollars in hospital bills.
If I could hop in the water and find a disc with my shoes on, that is easier, but those guys who walk around in stagnant, disgusting water barefoot scraping their foot along the bottom hoping to feel their disc, now that's just stupid imo.
I'm ranting now, but that's my feelings on this topic for the time being.