About 1m worth on each of two colours. The worst part of the task is (usually) data entry, it seems weird that these units are keypad entry only and have no computer interface*, but in this case data entry will be fairly simple as the labeling will be multiple repeats of the same short text.
However, I may have found a local solution so hold fire for a few days.
* I see the PT-E550W does have a USB interface. Heat-shrink tubing printing too... nice!