Re: whats a good distance
I am a relative newb, I have only been fishing rivers for for a few years. I fish the Truckee here in Reno, which is a pretty good sized freestone river and can have some pretty good flows, although right now it seems a fraction of its normal self. On a good day I can probably cast bank to bank, which is a pretty good cast for me, probably 60 to 70 feet.
Now when I am fishing the river, I pick my spots and I generally cast about 20 to 25 feet or so and let it drift through, I do this starting close to shore (where I am wading in) and then towards the middle in an upstream fan pattern, then I take a couple steps and do it again until I am in the middle of the river more or less. From there I can fish the far bank, working upstream, again I will fish a fan pattern on the river from center to edges. On the way out, I will turn around and fish a fan pattern back towards where I am going to exit.
Now, if you are fishing a big wide river or the curent is really fast and you cant wade out to the middle, you may need that 60 foot cast to hit a seam, but most of the time if you are casting that far (in my opinion), on a fast river, you are going to have difficulty getting a drag free drift accross all the changes in current and you better be good at mending or be throwing a bug you can strip accross current .
When I hear someone say I am casting 30 to 40 yards (no offense to the original poster cause I probably said it myself a time or two) I kind of chuckle. I have only once or twice (with a wind at my back on the lake) casted into my backing, and when you realize that most fly line is 90 feet (30 yards) and that in order to cast 30 yards of line you have to be into your backing, you start getting a better feel for just how far 30 yards is.
As others have said above, it is not how far you cast most of the time, it is the presentation of the fly, how well you can control the drift, getting it down to the right depth, making it look like a natural on the surface, etc. and while there may be times you need that 30 yard cast, most of those times I bet you would be better off finding another way to get a fly to those fish with a good drift. Maybe work your way around and accross and come back up the other bank? I have found I do not get a lot of shots at or catch many decent sized fish if I am casting full out and then dragging my line accross multiple seams and trying to keep my fly in the feeding lane.