Answer: The main stem of indeterminate types will grow up to 8 feet with lots of side shoots! The semi-indeterminate types and determinate ones are sometimes referred to as bush varieties. Their main growing stems stop growing earlier than indeterminate ones. As you have seen, vigorous determinates can still grow quite large. I usually stake or cage (or both!) all my tomatoes, both determinate and indeterminate. I think a trellis would work fine for both types--you'll see the plants' different growing habits as the season progresses.
Whatever system you use to train your tomatoes, be sure to use something soft to tie the stems. There are lots of different theories about pruning tomatoes, removing suckers, etc. I usually remove the suckers (the shoots that arise from where a leaf joins the stem) for the first part of the season, so I can establish a strong main stem.
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