How can you recognise that the electrolyte is used up?
The depletion of the electrolyte can be recognised by the slowing deposition. This can often also be recognised by the disappearing colour of the electrolyte. The lustre may also diminish.
Overall, it is therefore advisable to use a suitable metal anode. This dissolves slowly and enriches the electrolyte with the corresponding metal. However, the electrolyte becomes contaminated over time and brighteners (if present) are used up.
However, there are also electrolytes in which the anode does not dissolve (e.g. gold).