I use 2 rods as i feel any more and you don't give them your full attention - the 3rd being normally slung down a margin.
I have had the experience of 2 fish on at at the same time and must say while fun is very hectic.
One of the main reasons i went back to 2 rods was on a venue i was fishing a few years ago the fish seemed beat only to come alive again right under the tips, normally crashing through the other 2!!

Have you tried to sort out 3 rods in the dark and cold!!!!

Thats why it's been back to 2 for me