Well, let's calculate how efficient that is, eh?
Assuming six of every nymph, so 24 by 6 (6 upped, 6 unupped) = 144. So that's the number of nymphs we need.
Now multiply it by six, because we need six relics to get a nymph = 864.
Then multiply it by ten, because we have a 1 in 10 chance of getting a nymph by trading in six relics = 8640. 8640 relics are needed.
You gain 3 relics a win (Assuming you have 30 nymphs, which I question... A lot.), So divide 8640 and round up to get the approximate umber of games needed = 2880.
How many games have I played in my entire elements career? 3090. (I'm a bit casual, I'll admit.)
So... I question the actual efficiency of farming this way.
But hey, who knows? If we wanted to, we could factor in the average seconds to win against an AI, and connecting via pvp2, and then have an approximate number of seconds needed, which we can convert into hours (Should be more than a day.)