[PvK]

If you anticipate a storage, it usually makes sense to scrap or mothball ships down to the point that you will not run out of minerals... so you have control over what is deactivated, and construction can continue.

The exception is generally when you have a big fleet active which you really can't afford, and you prefer to keep it all active at the cost of having construction fail and a random ship or base disband.

PvK