I have the problem of bobbin thread ends cracked.
Plastic radiator pipe covers from Poundland (Dollar Store?) are really thin and can be cut into rings just the right width to cover the thread on the bobbin. The downside is that they are white and it's tricky to see the colour of the thread; which is why I keep them with their larger spool. I've heard of aquarium air pipe being used too, cutting the rings to open them to get them around the bobbin.