90% capacity is FULL CAPACITY.
Apart from some very rare occasions the need for contingency is essential.
If your organisation or your project or your life is running at 100%, don’t expect to do that for long.
Exhaustion, stress, fatigue, mechanical breakage will undoubtedly ensue without some form of capacity built in
90% is all you’ve got for the longer term, best to build some contingency into your 90%.
Blog Post Number - 2803