Fuel pressure is maintained in a good system for a few hours maybe in a few cases over night. System pressure is established in about a second when the pump starts.
It is not expected that the system will have pressure before a cold start. Its possible that in real cold starting that the quantity of fuel through the cold start valve could be restricted by not having full pressure at the beginning of cranking. If this were the case and was part of the problem cranking for a second or two then a pause would make some difference. I think you will find that it doesn't matter much to a properly functioning system.
Bosch Master, ASE Master, L1
33 years MB technician