As there are multiple types of meringues, I imagine the core of this question is really the effect of acid on egg white foaming.
According to KATERYNA LOMAKINA and KAMILA MÍKOVÁ writing in the Czeck Journal of Food Science, there is a moderately complex relationship between pH of the egg whites, and its foaming capacity (overrun) and the stability of the foam:
By the addition of a small amount
of 1N H2 SO4 or NaOH to the liquid egg white (pH values: 9.5, 8.6,
6.3, 4.7,
3.1, 1.0), NAKAMURA and SATO (1964b) obtained a great foaming capacity at the neutral and acidic pHs except at the exceedingly
acidic pH (pH 1.0). The foam stability was high at pH 8.6, the pH of
the natural egg white, and decreased with changing pH.
With an aqueous
egg albumen solution, HAMMERSHØJ and LARSEN (1999) established that
the foam overrun was the highest at pH 4.8 and the lowest at pH 10.7.
The foam stability against drainage was the best at pH 7.0 after 30
min, but on a long-term scale the foam at pH 4.8 was the most
resistant to drainage. This is the result of the more rigid behaviour
of the surface at pH 4.8 and the formation of small bubbles,
therefore a slow drainage of liquid from the foam, lower dynamic
surface tension causing the high overrun.
The conclusion is that you will get the most volume of foam at moderately acidic pH around 4.8, but the best stability of the foam once created at the alkaline pH of egg whites.
The moral seems to be that for stable egg foam, not to add acid.
Later in the article, they also indicate that volume can be increased without ill effects by adding up to 40% more water to the egg whites.
Also, adding sugar to the egg whites inhibits foaming, requiring more agitation to form the foam.
It should be easily usable in applications where the egg texture is not that important. Find a recipe which needs both eggs (not whipped) and a liquid, and add the liquid to the overwhipped egg until the foam has subsided. Add the yolks back in (such recipes generally call for whole eggs).
This should work with different types of griddle cakes: pancakes, waffles, crepes. Also with the liquid used to top moussaka etc., or the liquid used to create straciatella soups.
Best Answer
The sad fact is: you usually know it when, half an hour after you are done whipping it, it floats in a puddle of liquid.
The problem is that it actually continues changing after you have stopped whipping. So, you really have to learn what the previous stage looks like, and stop whipping when that is reached. That's why I don't whip to really stiff peaks myself, instead I whip to soft and continue a bit, but stop before they have crossed the border to stiff, and when I let it sit, I have stiff.
This is assuming that you are making French meringue. If you are making Italian, the hot syrup stabilizes the proteins so they don't expell the water afterwards, and it reduces the volume, so whipping it longer is OK there.