First off, they need I repeat NEED to be staked and caged, contained, trellised, something. I let mine do as they will and it was a disaster. There's vines and tomatoes all over the place!
Pruning is not only a good idea, I'm fairly certain it's necessary. I pulled one out today. One vine was almost 15 feet long, with no fertilizer or compost tea or ANYTHING. By almost I mean 14 feet 9 inches. I measured it seeing as I was all the way in the neighbors yard before the stupid thing came out of the ground! What's worse is ou can barely tell I removed one and now I can see just how tomatoes have been missed during picking when moving the other plants around
Good thing there's sod going in there or I would NEVER hear the end of how there's a million tomatoe plants sprouting in the yard!Next: One plant is enough. ONE. unless you are starting your own produce stand or booth at the farmers market ONE PLANT IS ENOUGH. I have now gotten four five gallon buckets of yellow pear tomatoes and there's more everyday. My neighbors no longer asnwer their doors when I appear with a bag
Really though, one plant will produce a LOT of little maters. I planted three. Not recommneded......And finally, don't believe any of the hooey you hear about how suseptible yellow pear plants are to disease. The crazy weather this year did holy heck to my garden. Mildew everywhere, wilt and spotting throughout. On everything BUT those stinking yellow pears!
I planted three thinking one or two might die. Not one leaf was damaged. No BER, no rotting, about one of every 20 or so had a split in it, if that, and honestly I think those ones just sat too long before picking.
Believe the seed catalog or seed packet when it says "prolific"!
yes! One is enough 
you shoulda made some yellow sauce with those beauties! Or some yellow salsa!!