Is this kind of abbreviation correct usage (e.g. 10sec pause, 12h race, 10yr lease, 6day penalty)? Or must these examples read "4 min egg, 10 sec pause" etc,?
According to this document which relates to technical publications:
Write the number in figures, followed by a nonbreaking space. Then write the prefix symbol and the unit symbol with appropriate capitalization and no spaces: 3.58 MHz, 2.2 μF, 75 Ω. Use nonbreaking spaces to prevent clumsy line breaks such as the break between 2.2 and μF above.
This rule is more honoured in the breach than in the observance.