I recall a post awhile ago, where some one said, if his fly lasts one fish he is happy.
Another post was rubber legs, so that it will be more durable.

I fished on the Holsloot the a week or so ago, and fished the same flies for 2 days, taking over 80 fish between the 2 flies.
The one was a Spider/soft hackle pattern(Partridge and Orange) tied on a jig hook with a bead and the other a Gold Bead PTN, with paint bristles for a tail.
After the all of the fish, the flies went back into the box, ready for the next trip.

I am wondering how long do you expect your flies to last, not counting losing them in the trees, break offs on big fish etc?
Do you "plan" or evaluate a fly to see how durable it will be?
or specificly tie certain methods so that it will last longer?