I'm also in z5 and I tried pruning suckers to a main stem just one year. The plants were pitiful and the yield was pitiful, so I wouldn't recommend pruning at all. Our short growing seasons are already tough enough. lol!

Thanks party-music. Are you talking about not pruning indeterminate or determinate varieties? I don't prune suckers off determinates either.

Zone 5 gardener here too. I actually take a middle-of-the-road approach; I prune out the first few suckers, just so the lower canopy of the plant isn't so "wide". Because remember, off of those suckers come more suckers, which are more lateral, and so on and so on. But once the plants are 3 feet tall or so I pretty much let 'em go unless a sucker is hanging out so far away from the stem that it is intruding on another's space. Then I am merciless:) Seriously, I think they've done studies that do not show any meaningful difference in fruit yield no matter what you do (with respect to @party_music50's experience of course)

I'm in about the same zone and I[m not much of a pruner either. One thing that you probably should do is to check any leaves that touch the ground. Clip them off at the stem if they are below the fruit truss, or trim them if they sprout out higher than that. You don't want splashback from the soil onto the leaves as that will introduce fungal infection into the plant.

Your plants look nice and healthy!

I don't prune either - other than for what has already been mentioned: to remove lower leaves that touch the ground and may invite disease, and so fruits don't come in contact with the ground.

Really, I think the lore about pruning is mostly to grow larger, but fewer tomatoes and stake them to a single pole more easily. Suckers don't harm the plants - I think they actually provide more nourishment and energy from the extra foliage - along with more fruits from the branches.

I cage my tomatoes with tomato ladders and use spiral stakes to support the branches as they grow longer.