Our lot are just in the process of going to packs on for T/O. Our way around the "pressure bump" was to take one pack on after thrust reduction and the other when clean.
Apparently the perennial argument is the cost of pack cycles and pack life versus the cost of fuel and engine life.
The ever changing equation of the price of fuel, and how you pay for engine time/power and maintaining the packs will determine which way the operator will want to go.
Some engineer/bean counter types might be able to elaborate further.