Heirlooms are almost always indeterminate plants, but their are also many different varieties of heirloom tomatoes. For container gardening, you may want to consider using [url=https://organicgardening.about.com/od/vegetablesherbs/f/tomatotypefaq.htm]determinate tomato plants vs indeterminate tomato plants.[/url]
There are advantages and disadvantages to each and it's not always easy to determine which they are from a seed packet. You'll have to look them up online to find out which they are in most cases. Simply stated, and you can read this in the linked article, determinate plants tend to grow to a set height and stop, they also tend to bear most of their fruit at once. Indeterminate tend to be more vine-like and tend to bear fruit over the coarse of the season, giving you a more steady production for a season long harvest. The pros and cons of each are somewhat obvious. Determinate may require little or no support. Indeterminate may require extensive support, especially if you never prune them and the suckers get out of hand, creating even more vines to contend with (you really want to avoid this and keep indeterminate varieties to no more than two main vines, otherwise, you will see that your tomatoes may be smaller or may not fully ripen at all).
Regarding your plants bending over... In some cases the bend will break the necessary nutrient tunnels through the stalk/vine. If you re-right the plant and support it, it may survive with no problem. However, there is no repairing it once the pathway for the plant to get water and nutrients is broken. The severity of the bend/break will determine their future.
I have 10 plants and only the Roma's are determinant. I know I'll be supporting the rest once they outgrow the cages.